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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Tube A has both ends open, while tube B has one end closed, otherwise they are identical. The ratio of fundamental frequency of tube A and B is : |
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Answer» `1 : 2` `therefore (v_(A))/(v_(B)) = 2 ` .THUS CORRECT choice is (b). |
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| 2. |
A 400 pF capacitor charged by a 100 V dc supply is disconnected from the supply and connected to another uncharged 400 pF capacitor calculate the loss of energy |
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Answer» SOLUTION :`U_i = 1/2 CV^2 = 1/2 QV = 2 xx 10^(-6) J` After connecting charged CAPACITOR to uncharged capacitor of same capacity 1/2 of the charge will flow ` THEREFORE U_f = 1/2 q. V = 1/2 (q/2) V = (qV)/(4) = 1 xx 10^(-6) J` Loss in energy ,` U_i - U_f = 1 xx 10^(-6) J` |
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| 3. |
The electric field of certain radiation is given by the equation E = 200 {sin (4pi xx 10^10)t + sin(4pi xx 10^15)t} falls in a metal surface having work function 2.0 eV. The maximum kinetic energy 2.0 eV. The maximum kinetic energy (in eV) of the photoelectrons is [Plank's constant (h) = 6.63 xx 10^(-34)Js and electron charge e = 1.6 xx 10^(-19)C] |
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Answer» 3.3 |
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| 4. |
A hollow conducting sphere of inner radius R and outer radius 2R has resistivity 'rho' a function of the distance 'r' from the centre of the sphere: rho=kr^(2)//R. The inner and outer surfaces are painted with a perfectly conducting 'paint' and a potential difference DeltaV is applied between the two surfaces. Then, as 'r' increases from R to 2R, the electric field inside the sphere |
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Answer» increases `E=(KR^(2))/R i/(pir^(2))` `E-(KI)/(pir)` |
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| 5. |
A galvanometer of resistance 3663Omega gives full scale deflection for a certain current i_(g). Calculate the resistance of the shunt which when joined to the galvanometer coil will result in 1/34 of the total current passing through the galvanometer. also finid the total resistnace of the galvanometer and the shunt. |
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| 6. |
A capacitor 1mF withstands a maximum voltage of 6KV while another capacitor 2mF withstands a maximum voltage of 4KV. If the capacitors are connected in series, the system will withstand a maximum voltage of (MNR) |
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Answer» 2 KV |
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| 8. |
The reverse biasing in 9 p-n junction diode: |
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Answer» DECREASES the POTENTIAL barrier |
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| 9. |
The radii of curvature R_(1) and R_(2) of an equiconvex lens is each 20 cm and the refractive index of the material is 1.5. Its focal length will be _________. |
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Answer» SOLUTION :Hint : Here `R_(1)=+20 CM, R_(2)=-20 cm and N = 1.5` `therefore (1)/(f)=(n-1)((1)/(R_(1))-(1)/(R_(2)))=(1.5-1)[(1)/((+20))-(1)/((-20))]=(1)/(20) or f=20cm` |
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| 10. |
The angle of scattering for zero value of impact parameter 'b' is________. |
| Answer» SOLUTION :`PIR ` RADIAN. | |
| 11. |
A proton of mass m and charge e is projected from a very large distance towards an alpha particle with velocity v. Intially, particle is at rest, but it is free to move. If gravity is neglected, then the minimum separation along the straight line of their motion will be |
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Answer» `e^(2)//4 piepsilon_(0) MV^(2)` |
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| 12. |
An object is placed on the surface of a smooth inclined plane of inclination theta. It takes time t to reachthe bottom. If the same object is allowed to slide down a rough inclined plane of inclination theta, it takes time nt to reach the bottom where n is a number greater than 1. The coefficient of friction mu is given by:- |
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Answer» `mu=tan theta(1-1/n^2)` If s be the distance travelled , then `s=1/2 g sin theta xx t_1^2` ….(i) On rough inclined plane : Acceleration , `a=(mg sin theta -muR)/m` or `a=(mg sin theta -mu mg cos theta )/m` `=g sin theta - mug cos theta` `therefore s=1/2 (g sin theta - mug cos theta )t_2^2`...(ii) From equations(i) and (ii) , `t_2^2/t_1^2=(sin theta)/(sin theta - mu cos theta )` But `t_2=nt_1 , therefore n^2=(sin theta)/(sin theta - mu cos theta)` or `mu=(n^2-1)/n^2 xx (sin theta)/(cos theta)` or `mu=(1-1/n^2) tan theta` |
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| 13. |
Are the nucleons fundamental particles, or do they consist of still smaller parts? One way to find out is to probe a nucleon just as Rutherford probed an atom. What should be the kinetic energy of an electron for it to be able to probe a nucleon? Assume the diameter of a nucleon to be approx. 10^(-15)m. |
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Answer» Solution :Yes, the nucleus (neutrons and protons) are fundamental particles. To RESOLVE two objects, say nucleus separated by distance d, the WAVELENGTH `lambda` of probing signal must be less than or equal to d. As `d=10^(-15)m`, THEREFORE to detect separates parts, if any, insides a NUCLEON, the electron must have a wavelength `lambdale10^(-15)m`. Now, `lambda=h/p or p=h/lambda` and Kinetic energy, `K=pc=(hc)/lambda=(6.63xx10^(-34)xx3xx10^(8))/(10^(-15))"joule"` `K=(19.89xx10^(-11))/(1.6xx10^(-19))EV ~=10^(9)eV=1GeV` |
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| 14. |
White light is incident on a soap film at an angle of sin^(-1(4)/(5)) and the reflected light on examination by the spectroscope shows dark bands. The consecutive dark bands corresponds to wavelength 6100 Å and 6000 Å. If the refractive index of the film is 4/3, calculate its thickness. |
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| 15. |
Cadmium amalgam is preparedby electrolysisof a solutionof CdCI_(2)usingof 4A bepassedinorder to perpare 10%byweightCd in theCd -Hg amalgamon cathode of 4.5 g Hg ? |
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Answer» 400 SEC `=0.5 , (Cd^(+2) + 2e^(-) to Cd)` `(0.5)/(112) xx 2 =( 4 xx t)/(96500)` `THEREFORE t= 215.40 sec` |
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| 16. |
Two identical slabs are welded end to end 20 cals of heat flows through it in 4 min. If the two slabs are now welded by placing them one above the other, and same heat is flowing through two ends under the same difference of temperature, the time taken is : |
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Answer» 1 MIN `t_(2)=t_(1)(A_(2)x_(2))/(A_(2)*x_(1))` when welded together the area becomes twice and LENGTH becomes HALF. `t_(2)=(4xxA_(1)((x_(1))/(2)))/(2A_(1)*x_(1))="1 min"`. Thus CORRECT choice is (a). |
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| 17. |
(A) : A charge, whether stationary or in motion produces a magnetic field around it. (R) : Moving charges produce only electric field in the surrounding space. |
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Answer» Both 'A' and 'R' are TRUE and 'R' is the CORRECT EXPLANATION of 'A'. |
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| 18. |
(A) : If a current has both ac and de components, then a dc ammeter used to measure this current will measure the average value of the total current. (R): The scale of a dc ammeter is unformly divided. |
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Answer» Both 'A' and 'R' are TRUE and 'R' is the CORRECT EXPLANATION of 'A'. |
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| 19. |
Is a large brake on a bicycle wheel more effective than a small one ? |
| Answer» Solution :So long as the normal REACTION remains unchanged, between the surfaces. Hence, if the breaking force is the same, it is EQUALLY effective WHETHER the brake is LARGE or small. | |
| 20. |
A radioacitve isotope has a half-life of T years. How long will it take the activity to reduce to (a) 3.125% , (b) 1% of its original value? |
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Answer» Solution :a `(A)/(A_0) = 3.125% = (3.125)/(100)` `(A_0)/A = 100/(3.125) = 32` `((A_0)/A) = 2^n i.e., 32 = 2^n` `n LOG 2 = log 32, n = (log 32)/(log 2) = 5` `t/T = n= 5, t = 5T` B. `A/(A_0) = 1/100, (A_0)/A = 100 = 2^n` `n log 2 = log 100` `t/T = n = ((log 100)/(log 2)) , :. t = 6.65 T`. |
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| 21. |
यदि f= {{5, 2), (6, 3)} तथा g = {{2, 5), (3,6)}, तब f तथा g के परास क्रमशः है |
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Answer» (5,3) तथा (2,3) |
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| 22. |
A parallel plate air capacitor is made using two square plates each of side 0.2 m, spaced 1 cm apart. It is connected to a 50V battery. (a) What is the capacitance ? (b) What is the charge on each plate ? (c) What is the energy stored in the capacitor ? (d) What is the electric field between the plates ? (e) If the battery is disconnected and then the plates are pulled apart to a separation of 2 cm, what are the answers to the above parts ? |
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Answer» Solution :` C_0 =(in _0A)/(d) =( (8.85xx 10 ^(-12) xx 0.2 xx 0.2 )/( 0.01) = 3.54xx 10^(-5) mu F ` (b)`Q_0 =C_0 V_0 = 3.54 xx 10^(-5)xx 50= 1.77 xx 10^(-3)mu C ` (c) ` U_0=(1)/(2)C_0 V_0^(2) =(1)/(2)xx ( 3.54xx 10^(-11) ) ( 50)^(2)= 4.42 xx 10 ^(-4) J` (d) ` E_0 =(V_0)/(d) =( 50) /( 0.01) = 5000 V //m ` If the battery is disconnected the charge on the capacitor plates remains constant while the potential DIFFERENCE between the plates can CHANGE. `C= (in _0A) /(d)=(C_0)/( 2) =1.77xx 10^(-5) mu F . ` ` Q= Q_0 1.77 xx 10^(3) mu C ` `V= (Q)/(C) =( Q_0)/(C_0//2) =2V_0` ` U= (1)/(2) CV^(2) =C_0 V_0^(1) =8.84 xx 10 ^(-3)J` ` E= (V)/(d) =(2V_0)/( 2d_0) =E_0 =5000 V//m` |
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| 23. |
Near point for a person having normal vision, D= …........ |
| Answer» Solution : 25 cm | |
| 24. |
A point source of light S is placed at the bottom of a vessel containg a liquid of refractive index 5//3. A person is viewing the source from above the surface. There is an opaque disc of radius 1 cm floating on the surface. The centre of the disc lies vertically above the source S. The liquid from the vessel is gradually drained out through a tap. What is the maximum height of the liquid for which the source cannot at all be seen from above? |
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Answer» `R=h/(SQRT(u^2-1))` `h=Rsqrt(u^2-1)` `=(1 cm)sqrt((5//3)^2-1)=4/3 cm` |
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| 25. |
A boy and a man carry a uniform rod of length L,horizontally in such a way that the boy gets (1)/(4)th of the load. If the boy is at one end, the distance of the man from the other end is : |
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Answer» L/4  `:.`TAKING momentum about center of gravity, we have `(-W)/(4)xxL/2+(3W)/(4)(L/2-x)=0` `(WL)/(4xx2)=(3W)/(4)(L/2-x)` `L/2=(3L)/(2)-3ximplies3x=(3L)/(2)-L/2implies3x=Limpliesx=L/3` |
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| 26. |
Emissivity of perectly black body is |
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Answer» 1 |
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| 27. |
Graph shows the variation of the number of radioactive atoms left undecayed with time. Find the time corresponding to N=N_0//3? |
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Answer» SOLUTION :We KNOW that `N=N_0e^(-lambdat)` `(2N_0)/3 = N_0 e^(-lambdat_0) rArr e^(lambdat_0) =3/2 rArr lambdat_0=ln(3//2)`…(1) ALSO, `N_0/3 =N_0 e^(-lambdat_1) rArr lambdat_1`=ln 3 `rArr t_1=1/lambda ln(3) = (t_0 ln(3))/(ln (3//2))` [From (i)] |
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| 28. |
The lines of force due to earth's magnetic field are ....... . |
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Answer» PARALLEL, straight and horizontal |
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| 29. |
A convex lens offocal length 20cm is places coaxially with a convex mirror of radius of curvature 20cm. The two are kept at 15 cm from each other. A point object lies 60cm in front of the convex lens. Draw a ray diagram to show the formation of the image by the combination. Determine the nature and position of the image formed. |
Answer» Solution : For the CONVEX lens `u = - 60cm, f = + 20CM` `(1)/( v) - ( 1)/( u ) = ( 1)/( f)` `( 1)/( v) - ( 1)/( - 60) = (1)/( 20)` ` ( 1)/(v) = ( 1)/( 20) - ( 1)/( 60) = ( 2)/( 60) = ( 1)/( 30)` `v = 30CM` For the convex mirror `u = + ( 30-15)cm = 15cm, f = + ( 20)/( 2) cm = 10cm ` `(1)/( v ) + ( 1)/( u ) = ( 1)/( f)` ` ( 1)/( V ) + ( 1)/.( 15) = ( 1)/( 10) ` `(1)/(v) = ( 1)/( 10) - (1)/( 15) = ( 3-2)/( 30) = ( 1)/( 30)` `v = 30cm` Final image is formed at the distance of 30cm from the convex mirror ( or 45 cm from the convex lens ) to the right of the convex mirror. The final image formed is a VIRTUAL image. |
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| 30. |
On strong heating a ferromagnetic substance becomes _____ |
| Answer» SOLUTION :PARAMAGNETIC | |
| 31. |
The concept of electric field is due to Faraday and now it is one of the central concepts in Physics. Can you see the electric fields? How can you detect the electric fields? |
| Answer» SOLUTION :No, we cannot see the ELECTRIC field. But it can be detected by the FORCE acting on a CHARGE. | |
| 32. |
Referring to the previous illustration, find the (a) what is the value of 8, whon R H? (b) What happens to the range when value greater than 45^(@)and less than 45^(@) ? |
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Answer» SOLUTION :(a)When R=H `R=u^(2)sin2theta//g`and `H=u^(2)SIN^(2)theta//2g` `alpha` or `theta=tan^(-1)(4)` (B)Range value remain same |
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| 33. |
In a positive feedback oscillator, the feedback voltage (signal) and the input signal (voltage) have a phase difference of |
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Answer» SOLUTION :`I_C` = 24 mA `THEREFORE 24=80/100 I_E therefore I_E= 24xx100/80`=30 mA `therefore I_B` = 30-24= 6 mA |
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| 34. |
The positively charged part of the atom possesses most of the mass in ......... (Rutherford's model/both the models.) |
| Answer» SOLUTION :both the MODELS | |
| 35. |
In a single-slit diffraction experiment, the width of the slit is reduced to half its original width. How would this afffect the size and intensity of the central maxima ? |
| Answer» SOLUTION :On reducing the SIZE of slit to one-half, the size of central MAXIMA will be doubled and the intensity will become `(1)/(4)`th of its PREVIOUS VALUE. | |
| 36. |
A block of mass 0.50 kg is moving with a speed of2.0 m s^(-1) on a smooth surface. It strikes another stationary block of mass 1.0 kg and then move together as a single body. The energy loss during the collision is |
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Answer» 0.16 J =Momentum before collision , `(m_1+m_2)V=m_1u_1+m_2u_2` (0.5 +1.0)v = 0.5 x 2.0 + 1.0 x 0 `v=1/1.5=2/3 m s^(-1)` Loss of ENERGY ,= `1/2m_1u_1^2-1/2(m_1+m_2)v^2`=0.67 J |
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| 37. |
The magnetic iduction at a point P on the axis of a short magnetic dipole is equal to the magnetic induction at point Q on the equator of a short magnetic dipole. Then the ratio of distance of P and Q from the centre of the dipole is : |
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Answer» 1.26 |
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| 38. |
An electron and a photon, each has a wavelength of 1.2Å What is the ratio of their energies ? |
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Answer» `1:10` |
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| 39. |
The origin of nuclear force between nucleons is due to the exchange of |
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Answer» Mesons |
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| 40. |
A ball is dropped vertically from a height of h onto a hard surface.If the ball rebounds from the surface with a fraction r of the speed with which it strikes the latter on each impact, what is the net distance traveled by the ball up to the 10^(th) impact ? |
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Answer» `2H(1-r^(10))/(1-r)` |
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| 41. |
A particle moves along x-axis and its displacement at any time is given by x(t) = 2t^(3) -3t^(2) + 4t in SI units. The velocity of the particle when its acceleration is zero is |
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Answer» `2.5 ms^(-1) ` Differentiating with respect to t we get `(dx)/(dt) = 6t^(2)-6t+4 or nu= 6t^(2)-6t+4 ( because(dx)/(dt)=nu)` …(i) Again differentiating with respect to t. `(d^(2)x)/(dt^(2))=12T -6` a=12t-6 `( because (d^(2)x)/(dt^(2))=a)` According to question 0=12t -6 , `t = (6)/(12)=(1)/(2)s` Putting the value of t in equation (i) we get `nu= 6xx((1)/(2))^(2)-6xx((1)/(2))+4 ` `= 6xx(1)/(4) -6xx(1)/(2)+4=(5)/(2)=2.5 ms^(-1)` |
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| 42. |
Two weights w_(1) and w_(2) are suspended to the two ends of a string passing over a smooth pulley. If the pulley is pulled up with acceleration g then find the tension in the string |
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Answer» Solution :TENSION = `(2m_(1)m_(2))/(m_(1)+m_(2))(G+a)=(2(w_(1))/(g)(w_(2))/(g))/((w_(1))/(g)+(w_(2))/(g))(g+g)=(4w_(1)w_(2))/(w_(1)+w_(2))` |
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| 43. |
Using the necessary circuit diagrams, show how the V-I characteristics of a p-n junction are obtained in (i) Forward baising (ii) Reverse biasing. |
| Answer» SOLUTION :From the study of the characteristics ofa PN JUNCTION it is clear that a p-n junction conducts when connected in forward bias and praclically does rnut ALLOW fluw ofa current when connected in reverse bias. This property of p-n junction is made USE of in rectification of an a.c. into a d.c. | |
| 44. |
A copperbar of massm rest atright angles to two parallelhorizontal l distanceapart. The rails are connected by aresistorR atone end and kept open at the other ends . Ther is auniformupwardmagnetic fields of induction B.Thebar is pulledaway from the closed endbya constantforce F. Calculate the terminal velocityof the bar when mu is the coefficientof frction between the rails and the bar. |
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Answer» |
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| 45. |
Metals have |
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Answer» zero RESISTIVITY |
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| 46. |
The image of a candle is formed by a convex lens on a screen. The lower half of the lens is painted black to make it completely opaque. Draw the ray diagram to show the image formation. How will this image be different from the one obtained when the lens is not painted black ? |
Answer» SOLUTION :The ray diagram showing IMAGE formation is given in Fig 9.39.  POSITION, nature and size of the image is same when half part of the lens is either painted black or not. HOWEVER, the intensity of the image is reduced when the lower half of the lens is painted black. |
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| 47. |
A body starts rotating from rest due to a couple of 20 Nm and completes 60 revolutions in one minute. The M.I. of the body is |
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| 48. |
Electric permittivity of free space is _________ |
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Answer» |
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| 49. |
A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is 'C' then the resultant capacitance is |
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Answer» NC |
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| 50. |
A circular coil of wire consisting of 100 turns, each of radius 4.0 cm carries a current of 0.40 A. What is the magnitude of the magnetic field B at the centre of the coil ? |
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Answer» Solution :For a CURRENT carrying thin circular COIL of radius R with N no. of IDENTICAL tightly wound turns, magnetic field produced at the centre is, `B=(mu_(0)NI)/(2R)` `thereforeB=((4pixx10^(-7))(100)(0.4))/((2)(0.08))` `thereforeB=pixx10^(-4)T=3.14xx10^(-4)T` |
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