45406 + Interview Questions in Physics in Class 12 Page 5 InterviewSolution

201.	At the initial moment the activity of a certain radionuclie totalled 650 particles per minute.What will be the activity of the preperation after half its half-life period?
Answer» <html><body><p></p>Solution :The <a href="https://interviewquestions.tuteehub.com/tag/activity-25667" style="font-weight:bold;" target="_blank" title="Click to know more about ACTIVITY">ACTIVITY</a> is proprotional to the number to the number of parent nuclei(assuming that the daughter is not radioactive). In half its half-life period, the number of parent nucli decrease by a factor <br/> `(2)^(-<a href="https://interviewquestions.tuteehub.com/tag/1-256655" style="font-weight:bold;" target="_blank" title="Click to know more about 1">1</a>//2)=(1)/(<a href="https://interviewquestions.tuteehub.com/tag/sqrt-1223129" style="font-weight:bold;" target="_blank" title="Click to know more about SQRT">SQRT</a>(2))` <br/> So activity decreases to `(<a href="https://interviewquestions.tuteehub.com/tag/650-331163" style="font-weight:bold;" target="_blank" title="Click to know more about 650">650</a>)/(sqrt(2))= <a href="https://interviewquestions.tuteehub.com/tag/460-317760" style="font-weight:bold;" target="_blank" title="Click to know more about 460">460</a>` particles per minute.</body></html>

Discussion

202.	After time 't' the height ‘y ’ of projectile is y = 8t - 5t^(2) and horizontal distance x = 6t if g=10 ms^(-2)1 , velocity of projectile at this instant is :
Answer» <html><body><p>10m/s<br/>8m/s<br/>6m/s<br/>4m/s</p>Solution :During <a href="https://interviewquestions.tuteehub.com/tag/projectile-1169321" style="font-weight:bold;" target="_blank" title="Click to know more about PROJECTILE">PROJECTILE</a>’s <a href="https://interviewquestions.tuteehub.com/tag/motion-1104108" style="font-weight:bold;" target="_blank" title="Click to know more about MOTION">MOTION</a><br/>`x=ucosthetat`<br/>`6t=ucosthetatimplies ucostheta=6impliesu_(x)=6ms^(-1)`<br/>Similarly `y=usinthetat-1/2g t^(2)`<br/>`<a href="https://interviewquestions.tuteehub.com/tag/8t-340101" style="font-weight:bold;" target="_blank" title="Click to know more about 8T">8T</a> - 5t^(2)=usinthetat-1/2g t^(2)`<br/>`implies usintheta=8impliesu_(y)=<a href="https://interviewquestions.tuteehub.com/tag/8ms-1930770" style="font-weight:bold;" target="_blank" title="Click to know more about 8MS">8MS</a>^(-1)`<br/>Now `u=sqrt(u_(x)^(2)+u_(y)^(2))=10ms^(-1)`</body></html>

Discussion

203.	Compare the intensities of maxima and minima in terms ofamplitude ratio
Answer» <html><body><p></p>Solution :a. <a href="https://interviewquestions.tuteehub.com/tag/intensity-1047474" style="font-weight:bold;" target="_blank" title="Click to know more about INTENSITY">INTENSITY</a> (maximum or minimum) `prop` <a href="https://interviewquestions.tuteehub.com/tag/bandwidth-14801" style="font-weight:bold;" target="_blank" title="Click to know more about BANDWIDTH">BANDWIDTH</a> <br/> <a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>. Intensity (maximum) `I_("<a href="https://interviewquestions.tuteehub.com/tag/max-546895" style="font-weight:bold;" target="_blank" title="Click to know more about MAX">MAX</a>")prop(a_(1)+a_(2))^(2)` <br/> Intensity (minimum) `I_("minimum")prop(a_(1)-a_(2))^(2)` <br/> `:.(I_("max"))/(I_("min"))=((a_(1)+a_(2))^(2))/((a_(1)-a_(2))^(2))`</body></html>

Discussion

204.	(A) : Range is the largest distance between a source and a destination upto which the signal is received with sufficient strength (R) :Use of repeater station to increase the range of communication
Answer» <html><body><p>Both 'A' and 'R' are true and 'R' is the <a href="https://interviewquestions.tuteehub.com/tag/correct-409949" style="font-weight:bold;" target="_blank" title="Click to know more about CORRECT">CORRECT</a> <a href="https://interviewquestions.tuteehub.com/tag/explanation-455162" style="font-weight:bold;" target="_blank" title="Click to know more about EXPLANATION">EXPLANATION</a> of 'A'. <br/>Both 'A' and 'R' are true and 'R' isnot the correct explanation of 'A'. <br/>A' is true abd 'R' <a href="https://interviewquestions.tuteehub.com/tag/false-459184" style="font-weight:bold;" target="_blank" title="Click to know more about FALSE">FALSE</a> <br/>A' is false and 'R' is false </p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a></body></html>

Discussion

205.	A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirro. The size of the image is approximately equal to
Answer» <html><body><p>`<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>((u-<a href="https://interviewquestions.tuteehub.com/tag/f-455800" style="font-weight:bold;" target="_blank" title="Click to know more about F">F</a>)/f)^(1//<a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a>)`<br/>`b(f/(u-f))^(1//2)`<br/>`b((u-f)/f)`<br/>`b(f/(u-f))^(2)`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :D</body></html>

Discussion

206.	A source emitting light of wavelength 480 nm and 600 nm is used in a double slit interference experiment. The separation between the slits is 0.25 mm and the interference is observed on a screen placed at 150 cm from the slits. Find the linear separation between the first maximum (next to the central maximum) corresponding to the two wavelengths.
Answer» <html><body><p>0.36 mm<br/>0.18 mm<br/>0.72 mm<br/>0.98 mm</p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/c-7168" style="font-weight:bold;" target="_blank" title="Click to know more about C">C</a></body></html>

Discussion

207.	Which one of the following is the property of a monochromatic, plane electromagnetic wave in free space ?
Answer» <html><body><p>Electric and magnetic fields have a phase <a href="https://interviewquestions.tuteehub.com/tag/difference-951394" style="font-weight:bold;" target="_blank" title="Click to know more about DIFFERENCE">DIFFERENCE</a> of `(<a href="https://interviewquestions.tuteehub.com/tag/pi-600185" style="font-weight:bold;" target="_blank" title="Click to know more about PI">PI</a>)/(2)` <br/>The energy contribution of both electric and magnetic fields are equal <br/>The direction of propagation is in the direction of <a href="https://interviewquestions.tuteehub.com/tag/e-444102" style="font-weight:bold;" target="_blank" title="Click to know more about E">E</a> <br/>The pressure exerted by the wave is the product of energy <a href="https://interviewquestions.tuteehub.com/tag/density-17451" style="font-weight:bold;" target="_blank" title="Click to know more about DENSITY">DENSITY</a> and the speed of the wave</p>Answer :B</body></html>

Discussion

208.	A ball is rising through a liquid with constant speed. The ratio of density of liquid to that of material of ball is 3 : 1. The ratio of viscous force to the weight of the ball is:
Answer» <html><body><p>`1:3`<br/>`2:1`<br/>`1:4`<br/>`4:1`</p>Solution :Here `6pietarv+4/3pir^(3)<a href="https://interviewquestions.tuteehub.com/tag/pg-591026" style="font-weight:bold;" target="_blank" title="Click to know more about PG">PG</a>` <br/> `=4/3pir^(3)3.p.g` <br/> or `6pietarv=4/3pir^(3)g(3p-p)` <br/> `F=6pietarv` <br/> `=4/3pir^(3)xx2p.g=8/3pir^(3)pg` <br/> Ratio `F/W=(8/3pir^(3)pg)/(4/3pir^(3)pg)=2/1` <br/> `therefore` <a href="https://interviewquestions.tuteehub.com/tag/correct-409949" style="font-weight:bold;" target="_blank" title="Click to know more about CORRECT">CORRECT</a> <a href="https://interviewquestions.tuteehub.com/tag/choice-915996" style="font-weight:bold;" target="_blank" title="Click to know more about CHOICE">CHOICE</a> is (<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>).</body></html>

Discussion

209.	A metallic square loop PQRS is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in Fig. If V_(P), V_(Q), V_(R) and V_(S) are the potentials of points P, Q, R and S then which of the following is an incorrect statement?
Answer» <html><body><p>`V_(P)=V_(Q)` <br/>`V_(P)gtV_(S)`<br/>`V_(P)gtV_(R)`<br/>`V_(S)=V_(R)`</p>Solution :<a href="https://interviewquestions.tuteehub.com/tag/since-644476" style="font-weight:bold;" target="_blank" title="Click to know more about SINCE">SINCE</a> entire <a href="https://interviewquestions.tuteehub.com/tag/loop-1079198" style="font-weight:bold;" target="_blank" title="Click to know more about LOOP">LOOP</a> is in magnetic field so no <a href="https://interviewquestions.tuteehub.com/tag/net-5194" style="font-weight:bold;" target="_blank" title="Click to know more about NET">NET</a> emf will be induced in the loop, hence no current will flow in the loop. <br/> so, `V_(P)=V_(Q), V_(S)=V_(R), V_(P)gtV_(S), V_(P)` <br/> `gtV_(R), V_(Q)gtV_(R`). <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/BMS_V05_MCA_E01_021_S01.png" width="80%"/></body></html>

Discussion

210.	Assertion : A galvanometer can be converted into a voltmeter by connecting hight resistance (Rh) in series with the galvanometer . Reason : The high resistance , R_(h) = V/I_(g) - R_(g) where , I_(g) tocurrent through galvanometer R_(g) toResistance of the galvanometer
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/assertion-384238" style="font-weight:bold;" target="_blank" title="Click to know more about ASSERTION">ASSERTION</a> and <a href="https://interviewquestions.tuteehub.com/tag/reason-620214" style="font-weight:bold;" target="_blank" title="Click to know more about REASON">REASON</a> are correct and Reason is the correct explanation of Assertion . <br/>Assertion and Reason are true but Reason is the <a href="https://interviewquestions.tuteehub.com/tag/false-459184" style="font-weight:bold;" target="_blank" title="Click to know more about FALSE">FALSE</a> explanation of the Assertion .<br/>Assertion is true but Reason is false .<br/>Assertion is false but Reason is true. </p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :N/A</body></html>

Discussion

211.	A black body at a temprature of 227^@C radiates heat at the rate of 5 cal/cm^2 sec. At the temperature of 727^@C the rate of heat radiated in cal/cm^2 sec is
Answer» <html><body><p>20<br/>80<br/>200<br/>500</p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a></body></html>

Discussion

212.	In oscillator circuit, presence of .........are necessary
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/r-611811" style="font-weight:bold;" target="_blank" title="Click to know more about R">R</a> and <a href="https://interviewquestions.tuteehub.com/tag/c-7168" style="font-weight:bold;" target="_blank" title="Click to know more about C">C</a><br/>R and L<br/>C and R<br/>both C and L</p>Answer :D</body></html>

Discussion

213.	Show a plot of variation of alternating emf versus time generated by a loop of wire rotating in a magnetic field.
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :<a href="https://interviewquestions.tuteehub.com/tag/magnetic-551115" style="font-weight:bold;" target="_blank" title="Click to know more about MAGNETIC">MAGNETIC</a> <a href="https://interviewquestions.tuteehub.com/tag/flux-993757" style="font-weight:bold;" target="_blank" title="Click to know more about FLUX">FLUX</a> <a href="https://interviewquestions.tuteehub.com/tag/versus-2323224" style="font-weight:bold;" target="_blank" title="Click to know more about VERSUS">VERSUS</a> <a href="https://interviewquestions.tuteehub.com/tag/time-19467" style="font-weight:bold;" target="_blank" title="Click to know more about TIME">TIME</a> <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/OSW_SP_PHY_XII_C07_E03_001_S01.png" width="80%"/></body></html>

Discussion

214.	What amount of heat is needed to raise the temperature of 2xx 10^(-2) kg of nitrogen at room temperature to raise itstemperature by 45^(@)C at constant pressure ? (Given molecular mass =28 and R=8.3" J mol"^(-1)K^(-1),C_(p)=7//2 R):
Answer» <html><body><p>`9.33 <a href="https://interviewquestions.tuteehub.com/tag/cal-412083" style="font-weight:bold;" target="_blank" title="Click to know more about CAL">CAL</a>`<br/>`93.3 J`<br/>`933.4 J`<br/>`933.3 cal`</p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :Number of moles `n=(m)/(M)=(20)/(<a href="https://interviewquestions.tuteehub.com/tag/28-299271" style="font-weight:bold;" target="_blank" title="Click to know more about 28">28</a>)=0.174` <br/> `C_(p) =(7)/(2) R=(7)/(2) xx8.3 J" mole"^(-1) K^(-1)` <br/> `Delta Q =n C_(p) <a href="https://interviewquestions.tuteehub.com/tag/xx-747671" style="font-weight:bold;" target="_blank" title="Click to know more about XX">XX</a> Delta T` <br/> `=0.714xx(7)/(2)xx8.3 xx45 J` <br/> `=933.4 J`. <br/> `therefore` Correct <a href="https://interviewquestions.tuteehub.com/tag/choice-915996" style="font-weight:bold;" target="_blank" title="Click to know more about CHOICE">CHOICE</a> is (c ).</body></html>

Discussion

215.	Modern telescopes prefer using suitable mirrors over using suitable lenses. Give two reasons for this preference.
Answer» <html><body><p></p>Solution :Modern telescopes prefer using concave mirror of large <a href="https://interviewquestions.tuteehub.com/tag/aperture-881724" style="font-weight:bold;" target="_blank" title="Click to know more about APERTURE">APERTURE</a> as the objective instead of convex lens due to the following reasons : <br/> (1) There is no chromatic aberration in a mirror. <br/> (2) If the mirror is a parabolic mirror then even spherical aberration is also removed. <br/> (3) Mechanical support of reflecting type telescope is easy to design and install because mirror weigh much <a href="https://interviewquestions.tuteehub.com/tag/less-1071906" style="font-weight:bold;" target="_blank" title="Click to know more about LESS">LESS</a> than a lens of equivalent optical quality. <br/> (4) It is possible to have telescope objective mirror of larger aperture. In this way we can design telescopes of <a href="https://interviewquestions.tuteehub.com/tag/higher-1022060" style="font-weight:bold;" target="_blank" title="Click to know more about HIGHER">HIGHER</a> <a href="https://interviewquestions.tuteehub.com/tag/resolving-2248888" style="font-weight:bold;" target="_blank" title="Click to know more about RESOLVING">RESOLVING</a> power and greater viewing <a href="https://interviewquestions.tuteehub.com/tag/range-1177030" style="font-weight:bold;" target="_blank" title="Click to know more about RANGE">RANGE</a>.</body></html>

Discussion

216.	Mass of photon moving with speed v is ……,m_(0) is rest mass of photon.
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/zero-751093" style="font-weight:bold;" target="_blank" title="Click to know more about ZERO">ZERO</a><br/>`(m_(0 ))/(<a href="https://interviewquestions.tuteehub.com/tag/sqrt-1223129" style="font-weight:bold;" target="_blank" title="Click to know more about SQRT">SQRT</a>(1-(c^(<a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a>))/(v^(2))))`<br/>`(m_(0))/(sqrt(1-(v^(2))/c^(2)))`<br/>infinite</p>Answer :C</body></html>

Discussion

217.	The wavefront of a distant source of unknown shape is approximately
Answer» <html><body><p>Spherical<br/>plane<br/>cylindrical<br/>elliptical</p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a></body></html>

Discussion

218.	One concave and one convex lens have same focal length. If they are kept in contact, combination behaves as .......
Answer» <html><body><p> <a href="https://interviewquestions.tuteehub.com/tag/concave-927978" style="font-weight:bold;" target="_blank" title="Click to know more about CONCAVE">CONCAVE</a> lens<br/>Convex lens<br/><a href="https://interviewquestions.tuteehub.com/tag/transparent-11320" style="font-weight:bold;" target="_blank" title="Click to know more about TRANSPARENT">TRANSPARENT</a> plane plate <br/>Curved surface</p>Solution :`1/f_1=1/f+1/f`<br/>`1/f_1=(1)/(-f)+1/f`[`because` For concave lens f is <a href="https://interviewquestions.tuteehub.com/tag/negative-570381" style="font-weight:bold;" target="_blank" title="Click to know more about NEGATIVE">NEGATIVE</a> and for convex lens f is positive]<br/>`therefore 1/f_1=0``thereforef_1=infty`<br/>`therefore` Transparent plane plate.</body></html>

Discussion

219.	Figure shown a particle P of mass m moving on a smooth circular wire of radius 5 cm beingacted upon by attractiveforce ( conservative in nature) directed towards O which is 3cm from C as shown in the figure and having magnitude 4/3 (m)/((OP)^(2)) dynes, find the minimum velocity which should be given to the particle at A so that it may complete the circle successfully . Neglect gravity.
Answer» <html><body><p> <br/></p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :<a href="https://interviewquestions.tuteehub.com/tag/1-256655" style="font-weight:bold;" target="_blank" title="Click to know more about 1">1</a> cm/s</body></html>

Discussion

220.	The distance between an object and its image produced by a converging lens is 0.72 m. The magnification is 2. What will be the magnification when the object is moved by 0.04 m towards the lens ?
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a><br/>4<br/>3<br/>6</p>Solution :(b) Given, `m = 2` "and the <a href="https://interviewquestions.tuteehub.com/tag/image-11684" style="font-weight:bold;" target="_blank" title="Click to know more about IMAGE">IMAGE</a> formed is <a href="https://interviewquestions.tuteehub.com/tag/real-1178490" style="font-weight:bold;" target="_blank" title="Click to know more about REAL">REAL</a>" <br/> `<a href="https://interviewquestions.tuteehub.com/tag/therefore-706901" style="font-weight:bold;" target="_blank" title="Click to know more about THEREFORE">THEREFORE</a> "For a real image" (1)/(f) = (1)/(v) + (1)/(u)` <br/> `or "" 1 + (1)/(m) = (u)/(f)` <br/> `rArr "" 1+ (1)/(2) = (u)/(f)` <br/> `rArr (3)/(2) = (0.72)/(f)`<br/> `or "" f = (0.72 xx 2)/(3) = 0.16m` <br/> As the object is moved by 0.04 m towards the <a href="https://interviewquestions.tuteehub.com/tag/lens-1071845" style="font-weight:bold;" target="_blank" title="Click to know more about LENS">LENS</a>, the new <br/> `mu_(1) = 0.72 - 0.04 = 0.68 m` <br/> Again real image is formed <br/> `rArr "" 1 + (1)/(m) = (u_(1))/(f)` <br/> `rArr "" (1)/(m) = (0.04)/(0.16)` <br/> `rArr "" m = 4`.</body></html>

Discussion

221.	The magnetic moment of a bar magnet is 45 Am^(2) and its length is 10 cm. Calculate the magnetic field induction at a point 10 cm away from the centre of the magnet on the axial line.
Answer» <html><body><p></p>Solution :Length of the magnet , 2l = 10 cm `= 10 xx 10^(-2)` m <br/> `implies l =5 xx 10^(-2) m` <br/> Distance of the <a href="https://interviewquestions.tuteehub.com/tag/point-1157106" style="font-weight:bold;" target="_blank" title="Click to know more about POINT">POINT</a> on axial line , d=10 cm <br/> `= 10 xx 10^(-2) m ` <br/> Magnetic moment, `M=<a href="https://interviewquestions.tuteehub.com/tag/45-316951" style="font-weight:bold;" target="_blank" title="Click to know more about 45">45</a> Am^(2)` <br/> `:.` Magnetic induction on the axial line of the <a href="https://interviewquestions.tuteehub.com/tag/bar-892478" style="font-weight:bold;" target="_blank" title="Click to know more about BAR">BAR</a> magnet is `B = (mu_0)/( 4 <a href="https://interviewquestions.tuteehub.com/tag/pi-600185" style="font-weight:bold;" target="_blank" title="Click to know more about PI">PI</a> ) (2MD)/((d^(2)-l^(2))^(2))` <br/> `B = (4 pi xx 10^(-7))/(4 pi) ( 2 xx 45 xx 10 xx 10^(-2))/([(10 xx 10^(-2))^(2) - ( 5 xx 10^(-2))^(2)]^(2))` <br/> ` = 16 xx 10^(-3) T `</body></html>

Discussion

222.	If the components of A are A_(x)=2 and A_(y)=3, and the components of B are B_(x)=-4 and B_(y)= 2, compute the components of each of the following vectors. (i) A+B (ii) A- B (iii) 2A (iv) A+ 3B
Answer» <html><body><p></p>Solution :(i) Using unit vector notation, `A= 2i - 3j and B= - <a href="https://interviewquestions.tuteehub.com/tag/4i-318769" style="font-weight:bold;" target="_blank" title="Click to know more about 4I">4I</a> + 2j`. Adding <a href="https://interviewquestions.tuteehub.com/tag/components-926700" style="font-weight:bold;" target="_blank" title="Click to know more about COMPONENTS">COMPONENTS</a>, we see that `A + B= (2+[-4])i+ ([-3]+2)j= 2i-j`. Therefore, the <a href="https://interviewquestions.tuteehub.com/tag/x-746616" style="font-weight:bold;" target="_blank" title="Click to know more about X">X</a> <a href="https://interviewquestions.tuteehub.com/tag/component-926634" style="font-weight:bold;" target="_blank" title="Click to know more about COMPONENT">COMPONENT</a> of the sum is `-2` and the y - components is `-<a href="https://interviewquestions.tuteehub.com/tag/1-256655" style="font-weight:bold;" target="_blank" title="Click to know more about 1">1</a>`. <br/> (ii) `A- B= (2i-3j)-(-4i+2j)=(2-[-4])i+(-3-2)j=6i-5j`. The x-component is 6 and the y-component is `-5`. <br/> (iii) `2A=2(2i-3j)=4i-6j`. 4 and `-6` are the x- and y-components, respectively.<br/> `(iv) A+3B=(2i-3j)+3(-4i+2j)=(2+3[-4])i+(-3+3[2])j=-10i+3j. -10 and 3` are the x- and y-components, respectively.</body></html>

Discussion

223.	x-rays mostly used in _____ to detect injuries etc.
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :photoeletric <a href="https://interviewquestions.tuteehub.com/tag/effect-966056" style="font-weight:bold;" target="_blank" title="Click to know more about EFFECT">EFFECT</a></body></html>

Discussion

224.	A 100 V battery, a 5.00 Vresistor, and a 10.0 H inductor are connected in series. After the current in th circuit has reached its maximum value.
Answer» <html><body><p>the power being supplied by the <a href="https://interviewquestions.tuteehub.com/tag/battery-893842" style="font-weight:bold;" target="_blank" title="Click to know more about BATTERY">BATTERY</a> is `20.0 <a href="https://interviewquestions.tuteehub.com/tag/w-729065" style="font-weight:bold;" target="_blank" title="Click to know more about W">W</a>`<br/>the power being delivered to the resistor is `20.0 W`<br/>the power being delivered t the inductor zero<br/>the energy <a href="https://interviewquestions.tuteehub.com/tag/stored-7260220" style="font-weight:bold;" target="_blank" title="Click to know more about STORED">STORED</a> in the magnetic filed of the indicator is `20.0 J`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :A</body></html>

Discussion

225.	A ring of mass m and radius r rotates about an axis passing through its centre and perpendicular to its plane with angular velocity omega. Its kinetic energy is
Answer» <html><body><p>`1/2mr^(<a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a>)<a href="https://interviewquestions.tuteehub.com/tag/omega-585625" style="font-weight:bold;" target="_blank" title="Click to know more about OMEGA">OMEGA</a>^(2)`<br/>`mromega^(2)`<br/>`mr^(2)omega^(2)`<br/>`1/2mromega^(2)`</p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :<a href="https://interviewquestions.tuteehub.com/tag/kinetic-533291" style="font-weight:bold;" target="_blank" title="Click to know more about KINETIC">KINETIC</a> energy =`1/2Iomega^(2)`, and for ring `I=mr^(2)`. Hence KE `=1/2mr^(2)omega^(2)`</body></html>

Discussion

226.	A bar magnet of magnetic moment M is kept in a uniform magnetic field of strength B makingan anglethetawith its direction the torque acting on it is
Answer» <html><body><p>`<a href="https://interviewquestions.tuteehub.com/tag/mb-546939" style="font-weight:bold;" target="_blank" title="Click to know more about MB">MB</a> <a href="https://interviewquestions.tuteehub.com/tag/cos-935872" style="font-weight:bold;" target="_blank" title="Click to know more about COS">COS</a> <a href="https://interviewquestions.tuteehub.com/tag/theta-1412757" style="font-weight:bold;" target="_blank" title="Click to know more about THETA">THETA</a>`<br/>`mb`<br/>`mb(1-cos theta)`<br/>`mb <a href="https://interviewquestions.tuteehub.com/tag/sin-1208945" style="font-weight:bold;" target="_blank" title="Click to know more about SIN">SIN</a> theta`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :D</body></html>

Discussion

227.	The incient light photon involved in the photoelectric emission phenomenon
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/completely-409686" style="font-weight:bold;" target="_blank" title="Click to know more about COMPLETELY">COMPLETELY</a> disappears.<br/>comes out with an <a href="https://interviewquestions.tuteehub.com/tag/increased-1040402" style="font-weight:bold;" target="_blank" title="Click to know more about INCREASED">INCREASED</a> frequency<br/>comes out with a <a href="https://interviewquestions.tuteehub.com/tag/decreased-7266469" style="font-weight:bold;" target="_blank" title="Click to know more about DECREASED">DECREASED</a> frequency<br/>comes out <a href="https://interviewquestions.tuteehub.com/tag/without-3281350" style="font-weight:bold;" target="_blank" title="Click to know more about WITHOUT">WITHOUT</a> any <a href="https://interviewquestions.tuteehub.com/tag/change-913808" style="font-weight:bold;" target="_blank" title="Click to know more about CHANGE">CHANGE</a> in frequency</p>Answer :A</body></html>

Discussion

228.	In a betatron the magnetic flux across an equilibrium orbit of radiusr = 25 cmgrowsduringthe acceleration time at paractically constantrate Phi = 5.0 Wb//s. In the process, theelectrons acquire an energy W = 25 MeV. Findthe numberof revolutionsmade by theelectronduring the acedeleration time andthe correspondingdistancecovered by it.
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :The increment is <a href="https://interviewquestions.tuteehub.com/tag/energy-15288" style="font-weight:bold;" target="_blank" title="Click to know more about ENERGY">ENERGY</a> per revoltion is `<a href="https://interviewquestions.tuteehub.com/tag/e-444102" style="font-weight:bold;" target="_blank" title="Click to know more about E">E</a> Phi`, sothe <a href="https://interviewquestions.tuteehub.com/tag/number-582134" style="font-weight:bold;" target="_blank" title="Click to know more about NUMBER">NUMBER</a> of revoltutions is, <br/> `<a href="https://interviewquestions.tuteehub.com/tag/n-568463" style="font-weight:bold;" target="_blank" title="Click to know more about N">N</a> = (W)/(e Phi)` <br/> The distancetraversed is, `s = 2pi rN`</body></html>

Discussion

229.	A copper rod of length 2m is rotated with a speed of 10 rps, in a uniform magnetic field of 1 tesla about a pivot at one end. The magnetic field is perpendicular to the plane of rotation. Find the emf induced across its ends
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :`e = 1/2 B omega l^2 = 1/2 B (2pi n)l^2 =<a href="https://interviewquestions.tuteehub.com/tag/pi-600185" style="font-weight:bold;" target="_blank" title="Click to know more about PI">PI</a> Bn l^2` <br/>` e = 3.14 <a href="https://interviewquestions.tuteehub.com/tag/xx-747671" style="font-weight:bold;" target="_blank" title="Click to know more about XX">XX</a> 1 xx <a href="https://interviewquestions.tuteehub.com/tag/10-261113" style="font-weight:bold;" target="_blank" title="Click to know more about 10">10</a> xx 2 xx 2 = 125.6 `volt</body></html>

Discussion

230.	Nanukaka had tied a huge ............. turban around his head.
Answer» <html><body><p>red<br/>orange<br/>yellow<br/>green</p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a></body></html>

Discussion

231.	Consider a sphere of radius R with charge density distributed as : rho( r) =kr, r le R =0 for r gt R (a) Find the electric field at all points r. (b) Suppose the total charge on the sphere is 2e where e is the electron charge. Where can two protons be embedded such that the force on each of them is zero. Assume that the introduction of the proton does not alter the negative charge distribution.
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :(a) Let us consider a sphere S of radius R and two hypothetic spheres of radius r < R and r > R. <br/> Electric field intensity for point r < R, <br/> `ointvecE.dvecS = 1/epsilon_(0) int rho dN` <br/> But volume, `V = 4/3 pir^(3)` <br/> `dV = 4/3 pi xx 3r^(2) dr` <br/> `dV = 4pir^(2)dr` <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/KPK_AIO_PHY_XII_P1_C01_E03_027_S01.png" width="80%"/> <br/> `therefore ointvecE.dvecS = 1/epsilon_(0) 4pikint_(0)^(r)r^(3)dr \|rho =kr\|` <br/> `therefore E=1/(4epsilon_(0)).kr^(2)` <br/> As charge density is positive it means the direction of `vecE` is radially outwards. Electric field intensity for point `r gt R`. <br/> `ointvecE.dvecS = 1/epsilon_(0)intrho dV` <br/> `therefore E=(kR^(4))/(4epsilon_(0)r^(2))`.........(1) <br/> Here, also the charge density is again positive. So, the direction of `vecE` is radially outward. <br/> (b) The two <a href="https://interviewquestions.tuteehub.com/tag/protons-1171004" style="font-weight:bold;" target="_blank" title="Click to know more about PROTONS">PROTONS</a> must be placed symmetrically on the opposite sides of the centre along a diameter. This can shown by the figure <a href="https://interviewquestions.tuteehub.com/tag/given-473447" style="font-weight:bold;" target="_blank" title="Click to know more about GIVEN">GIVEN</a> below.<br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/KPK_AIO_PHY_XII_P1_C01_E03_027_S02.png" width="80%"/> <br/> Charge on sphere, <br/> `q = int_(0)^(R)rho dN = int_(0)^(R)(kr)4pir^(2)dr` <br/> `therefore q=4pik R^(4)/4=2e` <br/> `therefore k = (2e)/(piR^(4))`........(2) <br/> The protons 1 and 2 are embedded at distance r from the centre of the sphere as shown, then attractive force on proton 1, due to charge distribution is, <br/> `F_(1) = eE = (-<a href="https://interviewquestions.tuteehub.com/tag/ekr-3617369" style="font-weight:bold;" target="_blank" title="Click to know more about EKR">EKR</a>^(2))/(4epsilon_(0))`.........(3) <br/> And <a href="https://interviewquestions.tuteehub.com/tag/repulsive-613883" style="font-weight:bold;" target="_blank" title="Click to know more about REPULSIVE">REPULSIVE</a> force on proton 1 due to proton 2 is, <br. e="" xx=""> Net force on proton 1. <br/> `F =F_(1) + F_(2)` <br/> `therefore F=[(-er^(2))/(4epsilon_(0)).(Ze)/(piR^(4)) + e^(2)/(16 pi epsilon_(0)r^(4))]` <br/> Thus, net force on proton 1 will be zero, when <br/> `therefore (er^(2)2e)/(4epsilon_(0)piR^(4)) = e^(2)/(16piepsilon_(0)r)` <br/> `therefore r=R/(8^(1//4))` <br/> Hence, the protons must be at a distance r from the centre.</br.></body></html>

Discussion

232.	A cylindrical disc of a gyroscope of mass m=15kg and radius r=5.0cm spins with an angular velocity omega=330rad//s. The distance between the bearings in which the axle of the disc is mounted is equal to l=15cm. The axle is forced to oscillate about a horizontal axis with a period T=1.0s and amplitude varphi_m=20^@. Find the maximum value of the gyropscopic forces exerted by the axle on the bearings.
Answer» <html><body><p></p>Solution :The <a href="https://interviewquestions.tuteehub.com/tag/moment-25786" style="font-weight:bold;" target="_blank" title="Click to know more about MOMENT">MOMENT</a> of inertia is `1/2mr^2` and angular momentum is `1/2mr^2omega`. The axis oscillates about a horizontal axis making an <a href="https://interviewquestions.tuteehub.com/tag/instantaneous-516608" style="font-weight:bold;" target="_blank" title="Click to know more about INSTANTANEOUS">INSTANTANEOUS</a> <a href="https://interviewquestions.tuteehub.com/tag/angle-875388" style="font-weight:bold;" target="_blank" title="Click to know more about ANGLE">ANGLE</a>. <br/> `varphi=varphi_m"sin"(2pit)/(T)` <br/> This <a href="https://interviewquestions.tuteehub.com/tag/means-1091780" style="font-weight:bold;" target="_blank" title="Click to know more about MEANS">MEANS</a> that there is a variable precession with a rate of precession `(dvarphi)/(dt)`. The <a href="https://interviewquestions.tuteehub.com/tag/maximum-556915" style="font-weight:bold;" target="_blank" title="Click to know more about MAXIMUM">MAXIMUM</a> value of this is `(2pivarphi_m)/(T)`. When the angle between the axle and the axis is at the maximum value, a torque `IomegaOmega` <br/> `=1/2mr^2omega(2pivarphi_m)/(T)=(pimr^2omegavarphi_m)/(T)` acts on it. <br/> The corresponding gyroscopic force will be `(pimr^2omegavarphi_m)/(lT)=90N`</body></html>

Discussion

233.	What the negative sign expresses?
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :oppositely by <a href="https://interviewquestions.tuteehub.com/tag/directed-440230" style="font-weight:bold;" target="_blank" title="Click to know more about DIRECTED">DIRECTED</a>.</body></html>

Discussion

234.	What is sharpness of resonance ? Derive equation of Q-factor
Answer» <html><body><p></p>Solution :Frequency of resonance is independent to resistance R but sharpness of resonance is inversely proportional to R. <br/> Sharpness of resonance `= ( omega_(0))/( <a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a> <a href="https://interviewquestions.tuteehub.com/tag/delta-947703" style="font-weight:bold;" target="_blank" title="Click to know more about DELTA">DELTA</a> omega)` <br/> `= ( omega_(0) 2 L )/( 2 xx R ) = ( omega_(0) L ) /( R )`but `( omega_(0) L )/( R ) ` is <a href="https://interviewquestions.tuteehub.com/tag/called-907796" style="font-weight:bold;" target="_blank" title="Click to know more about CALLED">CALLED</a> the quality factor Q of a circuit. <br/> `:.` Quality factor `Q = ( omega_(0) L )/( R )` <br/> `:. ( omega_(0))/( 2 Delta omega ) = Q = ( " Resonant frequency ")/( "<a href="https://interviewquestions.tuteehub.com/tag/bandwidth-14801" style="font-weight:bold;" target="_blank" title="Click to know more about BANDWIDTH">BANDWIDTH</a>") = ( omega_(0))/( omega_(2) - omega_(1))` <br/> `:. 2 Delta omega = ( omega_(0))/( Q)` where `omega_(2)` and `omega_(1)` are the frequency at the current amplitude of `(I_("rms") )_("max")` with a value of `(1)/( sqrt(2))`. <br/> So, larger the value of Q the smaller is value of `2 Delta omega` or bandwidth and <a href="https://interviewquestions.tuteehub.com/tag/sharper-7711972" style="font-weight:bold;" target="_blank" title="Click to know more about SHARPER">SHARPER</a> is the resonance. <br/> Putting`L = ( 1)/( omega^(2) C 0` <br/> `Q = ( omega_(0) xx 1 )/( R xx omega_(0)^(2) C )` <br/> `:. Q = ( 1)/( omega_(0) RC )`<br/> (1) For series LCR circuit, Q-factor, <br/> `Q = ( 1)/( R ) sqrt(( L )/( C )) = ( omega_(0) L )/( R ) = ( 1)/( omega_(0) CR )`<br/> (2) For parallel LCR circuit, <br/> `Q = ( V_(L ))/( V_(R )) ` or `( V _(C ))/( V_(R ))`<br/> If the resonance is less sharp not only is the maximum current less the circuit is close to resonance for a larger range `Delta omega` of frequencies and the tuning of the circuit will not be good. <br/> So, less sharp the resonance, less is selectivity of the current or vice versa.<br/> If quality is larger, means R is low or L is large the circuit is more sleective.</body></html>

Discussion

235.	Two sinusoidal currents are given by i_1 = 2 sin (omegat + pi/6) and i_2 = 10 sin (omegat - pi/4)The phase difference between them is :
Answer» <html><body><p>`<a href="https://interviewquestions.tuteehub.com/tag/30-304807" style="font-weight:bold;" target="_blank" title="Click to know more about 30">30</a>^@`<br/>`60^@`<br/>`<a href="https://interviewquestions.tuteehub.com/tag/75-334971" style="font-weight:bold;" target="_blank" title="Click to know more about 75">75</a>^@`<br/>`90^@`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :C</body></html>

Discussion

236.	If the electric flux entering and leaving an enclosed surface respectively is phi_(1) and phi_(2), the electric charge inside the surface will be
Answer» <html><body><p>`(phi_(2)-phi_(<a href="https://interviewquestions.tuteehub.com/tag/1-256655" style="font-weight:bold;" target="_blank" title="Click to know more about 1">1</a>))epsilon_(<a href="https://interviewquestions.tuteehub.com/tag/0-251616" style="font-weight:bold;" target="_blank" title="Click to know more about 0">0</a>)`<br/>`(phi_(1)+phi_(2))//epsilon_(0)`<br/>`(phi_(2)-phi_(1))//epsilon_(0)`<br/>`(phi_(1)+phi_(2))epsilon_(0)`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :A</body></html>

Discussion

237.	An electron and a proton have same speed. How are their wavelength related?
Answer» <html><body><p></p>Solution :We <a href="https://interviewquestions.tuteehub.com/tag/know-534065" style="font-weight:bold;" target="_blank" title="Click to know more about KNOW">KNOW</a> de <a href="https://interviewquestions.tuteehub.com/tag/broglie-402933" style="font-weight:bold;" target="_blank" title="Click to know more about BROGLIE">BROGLIE</a> `<a href="https://interviewquestions.tuteehub.com/tag/lambda-539003" style="font-weight:bold;" target="_blank" title="Click to know more about LAMBDA">LAMBDA</a>=(<a href="https://interviewquestions.tuteehub.com/tag/h-1014193" style="font-weight:bold;" target="_blank" title="Click to know more about H">H</a>)/(mv)`.i.e., `lambda prop (1)/(m)`. As <a href="https://interviewquestions.tuteehub.com/tag/proton-1170983" style="font-weight:bold;" target="_blank" title="Click to know more about PROTON">PROTON</a> is heavier than electron, wavelength of proton is less than that of electron.</body></html>

Discussion

238.	Find the magnetic induction at the point O of the following figures if the wire carrying a current I = 15A has the shapes shown here. The radius of the curved part R=5cm, the linear parts of the wire are very long.
Answer» <html><body><p><br/></p>Answer :a) `<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>=(mu_(<a href="https://interviewquestions.tuteehub.com/tag/0-251616" style="font-weight:bold;" target="_blank" title="Click to know more about 0">0</a>)I)/(4piR)sqrt(<a href="https://interviewquestions.tuteehub.com/tag/pi-600185" style="font-weight:bold;" target="_blank" title="Click to know more about PI">PI</a>^(2)+4)= 0.11 <a href="https://interviewquestions.tuteehub.com/tag/mt-566013" style="font-weight:bold;" target="_blank" title="Click to know more about MT">MT</a>, b) B=`(mu_(0)I)/(4piR)sqrt(2+2pi+pi^(2))`= 0.13mT, (<a href="https://interviewquestions.tuteehub.com/tag/c-7168" style="font-weight:bold;" target="_blank" title="Click to know more about C">C</a> ) B = `(mu_(0)I)/(8piR)sqrt(8 + 9pi^(2) = 0.15 mT</body></html>

Discussion

239.	When Sunita, a class XII student, came to know that her parents are planning to rent out the top floor of their house to a mobile company she protested. She tried hard to convince her parents that this move would be a health hazard. (i) Ultimately her parents agreed. (1) In what way can the setting up to transmission tower by a mobile company in a residential colony prove to be injurious to health? (2) By objective to this move the parents, what value did Sunita display? (3) Estimate the range of e.m. waves which can be transmitted by an antenna of height 20m. (Given radius of the earth = 6400 km).
Answer» <html><body><p></p>Solution :(1) A transmitting <a href="https://interviewquestions.tuteehub.com/tag/tower-1424155" style="font-weight:bold;" target="_blank" title="Click to know more about TOWER">TOWER</a> makes use of electromagnetic waves such as microwaves, exposure to which can cause sever health hazards like tumour and cancer. Also, the transmitting antenna operates on a very high power, so the risk of someone <a href="https://interviewquestions.tuteehub.com/tag/getting-2670847" style="font-weight:bold;" target="_blank" title="Click to know more about GETTING">GETTING</a> severely burnt in a residential area increases. <br/> (2) By <a href="https://interviewquestions.tuteehub.com/tag/objecting-7702532" style="font-weight:bold;" target="_blank" title="Click to know more about OBJECTING">OBJECTING</a> to this move to her parents, Sunita has <a href="https://interviewquestions.tuteehub.com/tag/displayed-7675136" style="font-weight:bold;" target="_blank" title="Click to know more about DISPLAYED">DISPLAYED</a> awarness towards the health and environment of her society. <br/> (3) Range of the transmitting antenna, <br/> `d=sqrt(2hR)` <br/> Here, h is the height of the transmitting antenna and R is the radius of the Earth. <br/> `R=6400km=64xx105m` <br/> `d=sqrt(2xx20xx64xx10^(<a href="https://interviewquestions.tuteehub.com/tag/5-319454" style="font-weight:bold;" target="_blank" title="Click to know more about 5">5</a>))=16,000m` <br/> `16km`</body></html>

Discussion

240.	Which of the following graphs represents the variation of activity (A) of a radioactive substance with time (t).
Answer» <html><body><p><img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/NIK_OBJ_PHY_P2_XII_C09_E01_271_O01.png" width="30%"/><br/><img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/NIK_OBJ_PHY_P2_XII_C09_E01_271_O02.png" width="30%"/><br/><img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/NIK_OBJ_PHY_P2_XII_C09_E01_271_O03.png" width="30%"/><br/><img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/NIK_OBJ_PHY_P2_XII_C09_E01_271_O04.png" width="30%"/></p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :A</body></html>

Discussion

241.	Light of certain frequency and intensity incident on a photosensitive material causes photoelectric effect. If both the frequency and intensity are doubled, the photoelectric saturation current becomes
Answer» <html><body><p>halved<br/>quadruple <br/><a href="https://interviewquestions.tuteehub.com/tag/unchanged-2316761" style="font-weight:bold;" target="_blank" title="Click to know more about UNCHANGED">UNCHANGED</a> <br/><a href="https://interviewquestions.tuteehub.com/tag/doubled-2592927" style="font-weight:bold;" target="_blank" title="Click to know more about DOUBLED">DOUBLED</a> </p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :<a href="https://interviewquestions.tuteehub.com/tag/conceptual-928163" style="font-weight:bold;" target="_blank" title="Click to know more about CONCEPTUAL">CONCEPTUAL</a></body></html>

Discussion

242.	A circular coil of closely wound N terns and radius r carriers a current I. Write the expressions for the following : (i) the magnetic field at its centre (ii) the magnetic moment of this coil
Answer» <html><body><p></p>Solution :(i) At centre `B_(C)=(mu_(<a href="https://interviewquestions.tuteehub.com/tag/0-251616" style="font-weight:bold;" target="_blank" title="Click to know more about 0">0</a>)Ni)/(<a href="https://interviewquestions.tuteehub.com/tag/2r-300472" style="font-weight:bold;" target="_blank" title="Click to know more about 2R">2R</a>).` <br/> Here, current in the coil is anticlockwise and the direction of magnetic field is <a href="https://interviewquestions.tuteehub.com/tag/perpendicular-598789" style="font-weight:bold;" target="_blank" title="Click to know more about PERPENDICULAR">PERPENDICULAR</a> to the plane of coil upward, but if the current in the coil is clockwise, then the direction of magnetic field will be perpendicular to the plane of coil downward. <br/> (ii) The magnetic field <a href="https://interviewquestions.tuteehub.com/tag/due-433472" style="font-weight:bold;" target="_blank" title="Click to know more about DUE">DUE</a> to a circular coil of radius <a href="https://interviewquestions.tuteehub.com/tag/r-611811" style="font-weight:bold;" target="_blank" title="Click to know more about R">R</a>, carrying current I at its centre is <br/> `B=(mu_(0) I)/(2r)` <br/> The direction of magnetic field is perpendicular to plane of coil, directed outward if current is anticlock wise and inward if current is clockwise.</body></html>

Discussion

243.	A cord is wound round the circumference of a wheel of radius r. The axis of the wheel is horizontal and its moment of inertia about this axis is I. A weight mg is attached to the end of the cord and is allowed to fall from rest. The angular velocity of the wheel, when the weight has fallen through a distance h, is
Answer» <html><body><p>`[(2gh)/(l+mr)]^(1//<a href="https://interviewquestions.tuteehub.com/tag/2-283658" style="font-weight:bold;" target="_blank" title="Click to know more about 2">2</a>)`<br/>`[(2mgh)/(I+mr^(2))]^(1//2)`<br/>`[(2mgh)/(1+2mr^(2))]^(1//2)`<br/>`(2gh)^(1//2)`</p><a href="https://interviewquestions.tuteehub.com/tag/answer-15557" style="font-weight:bold;" target="_blank" title="Click to know more about ANSWER">ANSWER</a> :<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a></body></html>

Discussion

244.	Assertion: Electromagnetic radiations are regarded as waves. Reason: Because they exhibit interference, diffraction and polarization under some suitable circumstances.
Answer» <html><body><p><a href="https://interviewquestions.tuteehub.com/tag/assertion-384238" style="font-weight:bold;" target="_blank" title="Click to know more about ASSERTION">ASSERTION</a> and Reason are correct and Reason is the correct explanation of Assertion.<br/>Assertion and Reason are <a href="https://interviewquestions.tuteehub.com/tag/true-713260" style="font-weight:bold;" target="_blank" title="Click to know more about TRUE">TRUE</a> but Reason is the <a href="https://interviewquestions.tuteehub.com/tag/false-459184" style="font-weight:bold;" target="_blank" title="Click to know more about FALSE">FALSE</a> explanation of the Assertion.<br/>Assertion is true but Reason is false<br/>Assertion is false but Reason is true</p>Answer :A</body></html>

Discussion

245.	A negatively charged oil drop is prevented from failing under gravity by applying a vertical electric field 100 Vm^(-1). If the mass of the drop is 1.6 xx 10^(-3)g the number of electrons carried by the drop is (g=10 ms^(-2))
Answer» <html><body><p>`<a href="https://interviewquestions.tuteehub.com/tag/10-261113" style="font-weight:bold;" target="_blank" title="Click to know more about 10">10</a>^(<a href="https://interviewquestions.tuteehub.com/tag/18-278913" style="font-weight:bold;" target="_blank" title="Click to know more about 18">18</a>)`<br/>`10^(<a href="https://interviewquestions.tuteehub.com/tag/15-274069" style="font-weight:bold;" target="_blank" title="Click to know more about 15">15</a>)`<br/>`10^(<a href="https://interviewquestions.tuteehub.com/tag/6-327005" style="font-weight:bold;" target="_blank" title="Click to know more about 6">6</a>)`<br/>`10^(<a href="https://interviewquestions.tuteehub.com/tag/12-269062" style="font-weight:bold;" target="_blank" title="Click to know more about 12">12</a>)`</p></body></html>

Discussion

246.	In a p - n junction diode , not connected to any circuit
Answer» <html><body><p>the potential is the same everywhere <br/>the p - type side has a higher potential than the n - type side <br/>there is an <a href="https://interviewquestions.tuteehub.com/tag/electric-967871" style="font-weight:bold;" target="_blank" title="Click to know more about ELECTRIC">ELECTRIC</a> <a href="https://interviewquestions.tuteehub.com/tag/field-987291" style="font-weight:bold;" target="_blank" title="Click to know more about FIELD">FIELD</a> at the junction directed from the n - type side to p - type side.<br/>there is an electric field at the junction directed from the p-type side to n - type side . </p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :At junction a potential barrier/depletion layer is formed with n - side at higher potential and p - side at <a href="https://interviewquestions.tuteehub.com/tag/lower-1080637" style="font-weight:bold;" target="_blank" title="Click to know more about LOWER">LOWER</a> potential . Therefore , there is an electric field at the junction directed from the n - side to p - side. <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/MOD_RPA_OBJ_PHY_C23_E02_002_S01.png" width="80%"/></body></html>

Discussion

247.	In the output characteristics, curve of an NPN transistor , ……….is about to be a constant near knee point .
Answer» <html><body><p>`I_(C)`<br/>`I_(<a href="https://interviewquestions.tuteehub.com/tag/b-387190" style="font-weight:bold;" target="_blank" title="Click to know more about B">B</a>)`<br/>`I_(<a href="https://interviewquestions.tuteehub.com/tag/e-444102" style="font-weight:bold;" target="_blank" title="Click to know more about E">E</a>)`<br/>`V_("<a href="https://interviewquestions.tuteehub.com/tag/cc-911065" style="font-weight:bold;" target="_blank" title="Click to know more about CC">CC</a>")`</p>Answer :A</body></html>

Discussion

248.	निम्नलिखित में से कोनसी संक्रियाएँ क्रम-विनिमय नियम का पालन नहीं करती है
Answer» <html><body><p>योगफल<br/>गुणनफल<br/>भागफल<br/>इनमे से कोई नहीं</p>Answer :<a href="https://interviewquestions.tuteehub.com/tag/c-7168" style="font-weight:bold;" target="_blank" title="Click to know more about C">C</a></body></html>

Discussion

249.	What fraction of hydrogen atoms is in the state with the principle quantum number n=2 at a temperature T=3000K?
Answer» <html><body><p></p>Solution :By Boltzmann formula <br/> `(N_(2))/(N_(1))=(g_(2))/(g_(1)) e^(DeltaE//kT)`. <br/> Here `DeltaE=` energy difference between `<a href="https://interviewquestions.tuteehub.com/tag/n-568463" style="font-weight:bold;" target="_blank" title="Click to know more about N">N</a>=1` and `n=2` <a href="https://interviewquestions.tuteehub.com/tag/states-1225920" style="font-weight:bold;" target="_blank" title="Click to know more about STATES">STATES</a> <br/> `=13.6(1-(1)/(<a href="https://interviewquestions.tuteehub.com/tag/4-311707" style="font-weight:bold;" target="_blank" title="Click to know more about 4">4</a>))eV=10.22eV` <br/> `g_(1)=2` and `g_(2)=8` (counting `2s` & `2P` states).Thus <br/> `(N_(2))/(N_(1))=4e^(-10.22xx1.602xx10^(-19)//1.38xx10^(-23)xx3000)=2.7xx10^(-17)` <br/> Explicity `<a href="https://interviewquestions.tuteehub.com/tag/eta-446786" style="font-weight:bold;" target="_blank" title="Click to know more about ETA">ETA</a>=(N_(2))/(N_(1))=n^(2)e^(-DeltaE//kT),DeltaE_(n)= ħR(1-(1)/(n^(2)))` <br/> for the nth excited state beacuse teh degeneracy of the state with principle quantum number `n is 2n^(2)`.</body></html>

Discussion

250.	Light of wavelength 589 nm is used to view an object under a microscope. The aperture of the objective has a diameter of 0.900 cm. Find What is the maximum limit of rewolution for this microscope Unsing visible light of any wavelength you desire.
Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :To obtain the smallest angle corresponding to the maximum limit of resolution, we have to use the shortest wavelength `(lambda= <a href="https://interviewquestions.tuteehub.com/tag/400-315233" style="font-weight:bold;" target="_blank" title="Click to know more about 400">400</a> <a href="https://interviewquestions.tuteehub.com/tag/nm-579234" style="font-weight:bold;" target="_blank" title="Click to know more about NM">NM</a>)` in the visible <a href="https://interviewquestions.tuteehub.com/tag/spectrum-1221793" style="font-weight:bold;" target="_blank" title="Click to know more about SPECTRUM">SPECTRUM</a>. <br/> Limiting angle of resolution <br/> `triangle <a href="https://interviewquestions.tuteehub.com/tag/theta-1412757" style="font-weight:bold;" target="_blank" title="Click to know more about THETA">THETA</a> = 1.22((400xx10^(-9)m)/(0.900xx10^(-2)m)) rad` <br/> `= 5.42xx 10^(-5)rad`</body></html>

Discussion

Explore topic-wise InterviewSolutions in Class 12.

At the initial moment the activity of a certain radionuclie totalled 650 particles per minute.What will be the activity of the preperation after half its half-life period?

After time 't' the height ‘y ’ of projectile is y = 8t - 5t^(2) and horizontal distance x = 6t if g=10 ms^(-2)1 , velocity of projectile at this instant is :

Compare the intensities of maxima and minima in terms ofamplitude ratio

(A) : Range is the largest distance between a source and a destination upto which the signal is received with sufficient strength (R) :Use of repeater station to increase the range of communication

A short linear object of length b lies along the axis of a concave mirror of focal length f at a distance u from the pole of the mirro. The size of the image is approximately equal to

Which one of the following is the property of a monochromatic, plane electromagnetic wave in free space ?

A ball is rising through a liquid with constant speed. The ratio of density of liquid to that of material of ball is 3 : 1. The ratio of viscous force to the weight of the ball is:

A metallic square loop PQRS is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in Fig. If V_(P), V_(Q), V_(R) and V_(S) are the potentials of points P, Q, R and S then which of the following is an incorrect statement?

Assertion : A galvanometer can be converted into a voltmeter by connecting hight resistance (Rh) in series with the galvanometer . Reason : The high resistance , R_(h) = V/I_(g) - R_(g) where , I_(g) tocurrent through galvanometer R_(g) toResistance of the galvanometer

A black body at a temprature of 227^@C radiates heat at the rate of 5 cal/cm^2 sec. At the temperature of 727^@C the rate of heat radiated in cal/cm^2 sec is

In oscillator circuit, presence of .........are necessary

Show a plot of variation of alternating emf versus time generated by a loop of wire rotating in a magnetic field.

What amount of heat is needed to raise the temperature of 2xx 10^(-2) kg of nitrogen at room temperature to raise itstemperature by 45^(@)C at constant pressure ? (Given molecular mass =28 and R=8.3" J mol"^(-1)K^(-1),C_(p)=7//2 R):

Modern telescopes prefer using suitable mirrors over using suitable lenses. Give two reasons for this preference.

Mass of photon moving with speed v is ……,m_(0) is rest mass of photon.

The wavefront of a distant source of unknown shape is approximately

One concave and one convex lens have same focal length. If they are kept in contact, combination behaves as .......

The distance between an object and its image produced by a converging lens is 0.72 m. The magnification is 2. What will be the magnification when the object is moved by 0.04 m towards the lens ?

The magnetic moment of a bar magnet is 45 Am^(2) and its length is 10 cm. Calculate the magnetic field induction at a point 10 cm away from the centre of the magnet on the axial line.

If the components of A are A_(x)=2 and A_(y)=3, and the components of B are B_(x)=-4 and B_(y)= 2, compute the components of each of the following vectors. (i) A+B (ii) A- B (iii) 2A (iv) A+ 3B

x-rays mostly used in _____ to detect injuries etc.

A 100 V battery, a 5.00 Vresistor, and a 10.0 H inductor are connected in series. After the current in th circuit has reached its maximum value.

A ring of mass m and radius r rotates about an axis passing through its centre and perpendicular to its plane with angular velocity omega. Its kinetic energy is

A bar magnet of magnetic moment M is kept in a uniform magnetic field of strength B makingan anglethetawith its direction the torque acting on it is

The incient light photon involved in the photoelectric emission phenomenon

A copper rod of length 2m is rotated with a speed of 10 rps, in a uniform magnetic field of 1 tesla about a pivot at one end. The magnetic field is perpendicular to the plane of rotation. Find the emf induced across its ends

Nanukaka had tied a huge ............. turban around his head.

What the negative sign expresses?

What is sharpness of resonance ? Derive equation of Q-factor

Two sinusoidal currents are given by i_1 = 2 sin (omegat + pi/6) and i_2 = 10 sin (omegat - pi/4)The phase difference between them is :

If the electric flux entering and leaving an enclosed surface respectively is phi_(1) and phi_(2), the electric charge inside the surface will be

An electron and a proton have same speed. How are their wavelength related?

Find the magnetic induction at the point O of the following figures if the wire carrying a current I = 15A has the shapes shown here. The radius of the curved part R=5cm, the linear parts of the wire are very long.

Which of the following graphs represents the variation of activity (A) of a radioactive substance with time (t).

Light of certain frequency and intensity incident on a photosensitive material causes photoelectric effect. If both the frequency and intensity are doubled, the photoelectric saturation current becomes

A circular coil of closely wound N terns and radius r carriers a current I. Write the expressions for the following : (i) the magnetic field at its centre (ii) the magnetic moment of this coil

Assertion: Electromagnetic radiations are regarded as waves. Reason: Because they exhibit interference, diffraction and polarization under some suitable circumstances.

A negatively charged oil drop is prevented from failing under gravity by applying a vertical electric field 100 Vm^(-1). If the mass of the drop is 1.6 xx 10^(-3)g the number of electrons carried by the drop is (g=10 ms^(-2))

In a p - n junction diode , not connected to any circuit

In the output characteristics, curve of an NPN transistor , ……….is about to be a constant near knee point .

निम्नलिखित में से कोनसी संक्रियाएँ क्रम-विनिमय नियम का पालन नहीं करती है

What fraction of hydrogen atoms is in the state with the principle quantum number n=2 at a temperature T=3000K?

Light of wavelength 589 nm is used to view an object under a microscope. The aperture of the objective has a diameter of 0.900 cm. Find What is the maximum limit of rewolution for this microscope Unsing visible light of any wavelength you desire.