45406 + Interview Questions in Physics in Class 12

1.	A concave lens of focal length 20 cm is placed at a distance of 35 cm from an object. Find the position of the image and its magnification.
Answer» Solution :Data supplied, f = - 20 CM, `""` u = - 35 cm ,V = ? ,m = ? `(1)/(f) = (1)/(v) - (1)/(u) "" (1)/(20) = (1)/(+ 35) + (1)/(v)` `(1)/(v) = (-1)/(20) + (-1)/(35) = (-35+ 20)/(20 XX 35) = (- 55)/(700) ""v = (-700)/(55) = - 12.73 ` cm ` m = (v)/(u) = (- 12.73)/(-3.5) = 0.3637 `

Discussion

2.	Calculate the value of I in the circuit given below.
Answer» SOLUTION :`I (1 + 2 + 3) = 3 + 2 = 5V` `I = 5 //6 A or I = 0.83 A`

Discussion

3.	the earth's atmosphere is richer in _____ radiations.
Answer» BLUE colour Ultraviolet rays Infra-red Visible Answer :C

Discussion

4.	A moving coil galvonometer of resistance R_G gives a full scale deflection when a current I_g flows through its coil. It can be converted into an ammeter of range 0 to I(I > I_g) when a shunt of resistance S is connected across its coil. If this galvanometer is converted into an ammeter of range 0 to 2I, find the expression for the shunt required in terms of S and and R_G.
Answer» Solution :If a moving coil galvonometer of resistance `R_G`gives full scale deflection for acurrent `I_g`, it can be converted into an ammeter of MAXIMUM range I by connecting a shunt of resistance S, where `S = (R_G . I_g)/(I - I_g) implies SI = (R_G + S) I_(g)"" ....(i)` To CONVERT the GIVEN galvonometer into an ammeter of maximum range 2I we shall connect a shunt of resistance `S.`, where `S. = (R_G CDOT I_g)/(2I- I_g) implies S.. 2I = (R_G + S.) I_(g) "" ....(ii)` From (ii) and (i), we get `(2S.)/(S) = (R_(G) + S.)/(R_G + S) implies S. = (S . R_g)/((S + 2R_g))`.

Discussion

5.	Two wires of the same material have their lengths in the ratio 3:2 , diameters in the ratio 3:2 and streching forces in the ratio 3:4 . What is the ratio of their extension
Answer» SOLUTION : `V_(e_1)/V_(e_2)=SQRT((M_1R_2)/(M_2R_2))=sqrt(R_1^3/R_2^3xxR_2/R_1=2/1`

Discussion

6.	A second's pendulum is placed in a space laboratory orbitinground the earth at a heightof 3R, where Ris the radius of earth. The time period of the pendulum is :
Answer» zero `(3)/(2)s` 4 s infinite. Solution :In SPACE ship the whole of gravity is used in providing necessary centripetal force. `:.` apparent ACCELERATION due to gravity is zero. Hence `T=2pi sqrt((l)/(g))` BECOMES infinite. Thus correct choice is (d).

Discussion

7.	A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in a Young's double-slit experiment. (a) Find the distance of the third bright fringe on the screen from the central maximum for wavelength 650 nm. (b) What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide?
Answer» SOLUTION :Here, `d=2mm=2XX10^(-3)m` D = 120 cm = 1.2 m `lamda_(1)=650nm=65xx10^(-8)m` `lamda_(2)=520nm=52xx10^(-8)m` (a) For `3^(rd)` BRIGHT fringe, `(x_(n)d)/(D)=nlamda` Here n=3 and so `(x_(n)d)/(D)=3lamda` `:.x_(3)=(3lamdaD)/(d)` `=((3)(650xx10^(-9))(120xx10^(-2)))/((2xx10^(-3)))` `=1.17xx10^(-3)m`

Discussion

8.	The modern means of communication has this advantage of _____, _____ and possibility of _____ over a long distance.
Answer» SOLUTION :SPEED, reliabillity, COMMUNICATING

Discussion

9.	The wavelength of Haline in hydrogen spectrum was found 6563 A^0 in the laboratory. If the wavelength of same line in the spectrum of a milky way is observed to be 6586 A^0, then the recessional velocity of the milky way will be
Answer» `0.105 XX 10^(6) MS^(-1)` `1.05 xx 10^(6) ms^(-1)` `10.5 ms^(-1)` NONE of these Answer :B

Discussion

10.	A circular coil of N-turns and of radius R is kept normal to a magnetic field given by B = B_(0) cos omegat. Deduce an expression for emf induced in this coil. State the rule which helps to detect the direction of induced current.
Answer» Solution :As given circular coil of N-turns and of radius R is placed in a UNIFORM magnetic field `B = B_(0) cos Omegat` acting perpendicular to the plane of the coil, hence, total magnetic flux linked with the coil will be `phi_(B) = N A B = N (PIR^(2))B_(0), cos omegat` Since the magnetic flux is continuously varying with time, hence induced emf set up in the coil will be `phi_(B) = (dphi_(B))/DT = - d/dt[Npi R^(2) B_(0) cos omegat]` `=- NpiR^(2)B_(0)d/dt[cos omegat] = piR^(2)N B_(0) OMEGA sin omegat` Obviously the induced emf is sinusoidal in nature (of the form `omega_(0) = piR^(2)NB_(0)omega`. Direction of induced current can be DETERMINED by applying Fleming.s right hand rule. For its statement, see Point Number 31 under the heading "Chapter At A Glance".

Discussion

11.	(A): An emf is induced in a closed loop where magnetic flux is varied. The induced electric field is not a conservative field (R): The line integral vecE.vec(dl) around the closed loop is non-zero
Answer» Both A and R are TRUE and R is the CORRECT explanation Both A and R are true but R is not the correct explanation of A A is true but R is false Both A and R are false Answer :A

Discussion

12.	Liquid oxygen remains suspended between two pole faces of a strong horse shoe magnet because it is
Answer» diamagnetic non-magnetic. PARAMAGNETIC ferromagnetic Solution :LIQUID OXYGEN is paramagnetic.

Discussion

13.	Draw current v/s frequency curve for a series RLC circuit and explain the different portions of the curve.
Answer» Solution :Across the PORTION of the curve AB, the capacitive reactance will be greater than the INDUCTIVE reactance, and it behaves as a capacitive circuit. Across the portion of the curve BC, the capacitive reactance will be less than the inductive reactance and the circuit behaves as an inductive circuit. Across the portion of the curve at `B,X_(L)=X_(C)`. The impedance will be equal to the DC resistance R and the circuit behaves as a RESISTIVE circuit.

Discussion

14.	The distnace between the diminished and the magnified images of slits for two position and d_1 and d_2 respectively. The distance between the virtual images of the slit is :
Answer» `d-(d_1)/d_2` `d = d_1d_2` `d=sqrt(d_1d_2)` `d=sqrt((d_1)/d_2)` ANSWER :D

Discussion

15.	Refractive index of a thin convex lens is 1.5 and radii of curvature is 20 cm. The parallel rays incident on it intersect at distance .d., then d = ...... cm.
Answer» `(20)/(3)` 10 20 40 Solution :`1/f=1/d=(mu-1)(1/R_1-1/R_2)` `therefore1/d=(1.5-1)((1)/(20)+(1)/(20))` `therefore1/d=(0.5)/(10)` `therefored=20` CM

Discussion

16.	One coil with 40 turns and 4 "cm"^2 area of cross-section is kept perpendicular to one uniform magnetic field of flux density B. When this loop is pulled out of magnetic field suddenly, 2 xx 10^(-4) C electric charge flows through it. If resistance of this coil is 80Omega then B= ____ "Wb/m"^2.
Answer» 0.5 1 1.5 2 Solution :`Q=(DELTAPHI)/R` `=(NAB)/R` `therefore B=(QR)/(NA)` `=(2xx10^(-4)xx80)/(40xx4xx10^(-4))` `therefore B=1 "Wb/m"^2`

Discussion

17.	There are two spheres of same mass and radius. One is solid and the other is hollow. Which of them has a larger moment of inertia about a diameter ?
Answer» Solution :When know that `I=sum(mr^2)`, i.e. MOMENT of inertia of a body not only DEPENDS on mass but also depends UPON the DISTRIBUTION of mass from the axis of rotation.

Discussion

18.	In a Young double slit experiment, the width of the source slit is increased then……
Answer» instead of interference, diffraction appears fringe pattern GETS more and more sharp angular DISTANCE between fringes increased. fringe pattern gets less and less sharp. Solution :KNOWLEDGE based question

Discussion

19.	A circular coil of N turns and radius R carries a current I. It is unwound and rewound to make another coil of radius R/2, current I remaining the same. Calculate the ratio of the magnetic moments of the new coil and the original coil.
Answer» Solution :Magnetic moment of original COIL of N turns and RADIUS R carrying a current I `m_1 = N_1 A_1 I = N.PI.R^2.I` When the coil is unwound and is rewound to make another coil of radius `R_2 = (R_1)/2 = R/2` , the TOTAL number of turns in the coil will CHANGE to `N_2 = 2 N_1 = 2N`. As same current I flows through the coil even now, hence new magnetic moment is given by `m_2 = N_2 A_2 I = 2 N . pi . (R/2)^(2) . I = 1/2 N pi R^2 I = (\|vecm_1\|)/(2)`

Discussion

20.	What are the three chief uses of ‘studies’?
Answer» INTELLIGENCE, ornamentation, discourse Intelligence, DELIGHT, Distilled books Delight, ornament, ability Delight, FUN, judgment Answer :C

Discussion

21.	A convex lens produces an image of a condle flame upon a screen whose distance from candle is D. When the lens is displaced through a distance x, (the distance between the candle and the screen is kept constant), it is found that a sharp image is again produced upon the screen. Find the focal length of the lens in terms of D and x .
Answer» SOLUTION :`a+b=D b-a=X 2 b =D + x` `b =(D+x)//2A=(D-x)//2` `(1)/(b)-(1)/(-a)=(1)/(f) RARR (2)/(D+x)+(2)/(D-x)=(1)/(f)` `_(2).(D-x+D+x)/(D^(2)-x^(2))=(1)/(f) rArr(4D)/(D^(2)-x^(2))=(1)/(f) rArr f=(D^(2)-x^(2))//4D Ans.]

Discussion

22.	The plates of a parallel plate capacitor have area 2 m^2 each and are 10 cm. apart. If the charge on each plate is 8.85xx10^-12C, the electric field at a point:
Answer» Between the PLATES will be zero Outside the plates will be maximum Between the plates will CHANGE from POINT to point Between the plates will be 50 `N//C` ANSWER :D

Discussion

23.	A beam of radio active radiation is unaffected in a combined electric and magnetic field in mutually perpendicular direction. A boy argues that, it is essentially a gamma ray. Do you agree with him. Justify your answer.
Answer» Solution :It NEET not beray. It can be ` ALPHA or BETA` RAY as the electric and magnetic field are in mutually prependicular direction.

Discussion

24.	How the self-inductance of a coil depends on number of turns in the coil ?
Answer» Solution :Directly proportional to SQUARE of NUMB er of TURNS.

Discussion

25.	A n-p-n transistor conducts when
Answer» both COLLECTOR and emitter are POSITIVE with RESPECT to the base collector is positive and emitter is NEGATIVE with respect to the base collector is positive and emitter is at same potential as the base both collector and emitter are negative with respect to the base Answer :B

Discussion

26.	An em wave is propagating in a medium with a velocity vec(V)=V hat(i). The instantaneous oscillating electric field of this em waves is along + y axis. Then the direction of oscillating magnetic field of the em wave will be along
Answer» `-X` direction `-z` direction `-y` direction `+z` direction Solution :`VEC(V)=vec(E )xx vec(B)` `therefore hat(i)=hat(j)xx hat(K)` `therefore` Direction of `vec(B)` is in `+z` direction.

Discussion

27.	The width of spectral lines (spreading of spectral line) can be explained by -
Answer» Kirchoff’s radiation law DOPPLER’s EFFECT Spin motion of ELECTRONS Stark’s effect Answer :B

Discussion

28.	In the circuit shown in the figure, the power dissipated in the circuit is P_(0) if an ideal cell is connected across A and B. Same power is dissipated in the circuit if the same cell is connected across C and D. When the cell was connected across A and D or across B and C, the power dissipated in the circuit is found to be 3P_(0). Calculate the power dissipated in the circuit if the cell is connected across A and C.
Answer» <P> ANSWER :`((15+6sqrt(7))/(16+6sqrt(7)))P_(0)`

Discussion

29.	A copper rod of length 2m is rotated with a speed of 10 rps, in a uniform magnetic field of T tesla about a pivot at one end. The magnetic field is perperndicular to the plane of rotation. Find the emf induced across its ends
Answer» Solution :`e=(1)/(2)B omega l^(2)=(1)/(2)B(2PI N)l^(2)=pi BNL^(2)` `e=3.14 XX 1 xx 10 xx 2 xx 2=125.6` volt

Discussion

30.	A charge q_(0) is movedfrom point P to point q along the arc PQ with centre at O as shown in the figure near a long charged wire. The linear charge density of the wire is lambda and it in the same plane. Find the work done in the process.
Answer» Solution :We know that electric field is conservative. So work doen does not dependupon the PATH. `W_(P to Q) =W_(P to O) ( :. V_(0)=V_(Q))` `W_(P to Q) = -int_((r+D))^(D ) q barE . dbarr` `W= -q int_((r+D))^(D) (2lambda)/(4pi in_(0)) (dr)/(r ) =(lambdaq)/(2pi in_(0)) log_(e ) ((r+D)/(D)).`

Discussion

31.	Symbol Q stands for energy released
Answer» ANSWER :A::B::C::D

Discussion

32.	A moving coil galvanometer experience torque=ki, where iis current. IfN coils of area Aeach and moment of inertiaI is kept in magnetic field B. (i) If for current i deflection is (pi)/2, the torsional constant of spring is (x BiNA)/(pi). Find x^2 (ii) If a charge Q is passed suddenly through the galvanometer, the maximum angle of deflection is Qsqrt((BNpiA)/(xI)). Find x^2
Answer» Answer :(i) 2(ii) 2Solution :(i) 2 (ii) 2 (i) `tau=k.theta=BiNa:.k=(2BiNa)/(pi) ` (as `theta=pi//2)` (ii) `tau=BiNA` or `int_(0)^(t) taudt=BNA int_(0)^(t)IDT, I omega =BNAQ`, or `omega=(BNAQ)/I` At maximum deflection, whole kinetic energy (rotational) will be CONVERTED into potential energy of spring. Hence `1/2 I omega^(2)=1/2 k theta_("max")^(2),` Substituting the VALUES the values we get `, theta_("max")=Qsqrt((BNpiA)/(2I))`

Discussion

33.	Compare the electrical conductivity of pure germanium at -40^(@)Cand+100^(@)C. The activation energy for germanium is 0.72 eV
Answer» Solution :The mean free path of the electron is much LESS dependent on the TEMPERATURE than the exponential term, therefore the temperature dependence of the factor B can be NEGLECTED in the FIRST approximation. We have `gamma_(2)/gamma_(1)=(e^(-Deltaepsi//kT_(2)))/(-Deltaepsi//kT_(1))=exp{(Deltaepsi(T_(2)-T_(1)))/(kT_(1)T_(2))}`

Discussion

34.	If lower half of a concave mirror is blackned then
Answer» IMAGE distance increases image distance DECREASES image INTENSITY increases image intensity decreases Solution :Because of doing so, APERTURE decreases and so, less no. of light rays PRODUCE the image and so intensity of image decreases.

Discussion

35.	A : In interference, the fringe obtained at the centre of the screen is known as zeroth order fringe, or the central fringe R : In interference, path difference between the waves from S_(1)" and "S_(2), reaching the central fringe (or zero order fringe) is zero
Answer» Both A and R are TRUE and R is the CORRECT EXPLANATION of A Both A and R are true and R is not the correct explanation of A A is true and R is false Both A and R are false Answer :A

Discussion

36.	A cell of emf epsilon and internal resistance (r) is connected in series with an external resistance (nr)then the ratio of the terminal potential difference to emf is:
Answer» SOLUTION :`V=epsilon-ir=epsilon-(EPSILONR)/(r_nr)`

Discussion

37.	The charges on three dentical ebonite spheres are +2 mC, -4 mCand +2 mC respectively. Now the first sphere is brought in contact with the second sphere and then moved apart. Then, the second sphere is brought in contact with the third sphere and moved apart. Calculate the charge acquired by each sphere, provided ench sphere is kept on an insulated stand.
Answer» SOLUTION :`-1 MC, 1/2 mC` and `1/2` mC

Discussion

38.	A dices of mass M and radius R rolls without slipping on a leveled surface with a linear speed v. what is its kinetic energy?
Answer» `3/7Mv^2` `4/3Mv^2` `2 Mv^2` `3/4 Mv^2` ANSWER :A

Discussion

39.	(a) Determine the number of carbon ._6^(14)C atoms present for every gram of carbon ._6^(12)C in a living organism. Find (b) The decay constatnt and (c ) the activity of this sample.
Answer» Solution :The total number of carbon `._6^(12)C` atoms in onegram of carbon `._6^(12)C` is equal to the corresponding number od moles times Avogadro's number. Since there is only one `._6^(14)C` atom for every `8.3 xx 10^(11)` atoms of `._6^(12)C`, the number of `._6^(14)C` atoms is equal to the number of `._6^(12)C` atoms divided by `8.3 xx 10^(11)` . The decay constant `lambda` for `._6^(14)C` is `lambda =0.693//T_(1)//2`, Where `T_(1)//2` is the half-life. The activity is equal to the magnitude of `DELTA N//Delta t`, which is the decay constant times the number of `._6^(14)C` atoms present. (a) One gram of carbon `._6^(12)C` (atomic mass` = 12 u`) is equivalent to `1.0//1.2 mol`. Since Avogardo's number is `6.02 xx 10^(23)` atoms `mol^(-1)`and sinceof `._6^(14)C` atom for every `8.3 xx 10^(11)` atoms of `._6^(12)C` the number of `._6^(14)C` atoms FRO every `1.0 g` of carbon `._6^(12)C` is `((1.0)/(2)mol)(6.02 xx 10^(23) (("atoms")/(mol))((1)/(8.3 xx 10^(11)))` `=6.0 xx 1-^(10)` atoms (B) Since the half - life of `_(6)^(14)C` is `7530 ` years `(1.81 xx 10^(11) s)`, the decay constant is `lambda =(0.693)/(T_(1)//2) =(0.693/(1.81 xx10^(11) s)) =-3.83 xx 10^(-12) s^(-1)` (c ) The activity is the magnitude of `Delta N//Delta t` or `lambda N`. Thus, we find activity of `._6^(14)C` for every `1.0 g` of carbon `._6^(12)C` in a living organism`=lambdaN=(3.83xx10^(12)s^(-1))(6.0 xx10^(10)"atoms" )=0.23 Bq`. An organism that lived thousands of years ago presumbly had an activity of about `0.23 Bq` per gram of carbon. When the organism died, the activity began decreasing. From a sample of the remains, the current activity per gram of carbon can be measured and COMPARED to the value of `0.23 Bq` to determine the timethat has transpired since death.

Discussion

40.	Consider a coin, It is electrically neutral and contains equal amounts of positive and negative charge of magnitude 34.8 kC. Suppose that these equal charges were concentrated in two point charges separated by (i) 1cm (~(1)/(2)xxdiagonal of the one paisa coin) (ii) 100 m (~length of a long building) (iii) 10^(6)m (radius of the earth). find the force on each such point charge in each of the three cases. what do you conclude from these results?
Answer» Solution :Here, `q=+-34.8RC=+-3.48xx10^(4)C` `r_(1)=1cm=10^(-2)m,r_(2)=100m,r_(3)=10^(6)m and (1)/(4piepsi_(0))=9xx10^(9)` `F_(1)=(\|q\|^(2))/(4piepsi_(0)r_(1)^(2))=(9xx10^(9)(3.48xx10^(4))^(2))/((10^(-2))^(2))=1.09xx10^(23)N` `F_(2)=(\|q\|^(2))/(4piepsi_(0)r_(2)^(2))=(9xx10^(9)(3.48xx10^(4))^(2))/((100)^(2))=1.09xx10^(15)N` `F_(3)=(\|q\|^(2))/(4piepsi_(0)r_(3)^(2))=(9xx10^(9)(3.48xx10^(4))^(2))/((10^(6))^(2))=1.09xx10^(7)N` Conclusion from this result we observe that when `+-`charges in ordinary neutral MATTER are separated as POINT charges, they exerted an ENORMOUS force. HENCE, it is very difficult to distrub electrical neutrality of matter.

Discussion

41.	A particle starts from the origin at t0s with a velocity of 10.0hatj m/s and moves in the X-y plane with a constant acceleration of (8hati +2hatj) ms^(-2). The y-coordinate of the particle in 2 sec is
Answer» 24 m 16 m 8 m 12 m Answer :A

Discussion

42.	In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole ?
Answer» Solution :At the poles, earth's FIELD is exactly VERTICAL. As the compass NEEDLE is free to ROTATE in a horizontal plane only, it MAY point out in any direction.

Discussion

43.	A manometer connected to a closed tap reads 4.5 xx 10^5 Pa. When the tap is opened, the reading of the manometer falls to 4 × 10^5pascal. Then the velocity of flow of water is
Answer» a)`7 m s^-1` b)`8 m s^-1` C)`9 m s-1` d)`10 m s^-1` Answer :D

Discussion

44.	Obtain the mass of an electron in hydrogen atom in terms of its orbital period and radius of orbit.
Answer» Solution :The required centripetal FORCE of the electron in the hydrogen ATOM is provided by the coulomb force, `:. (mv^(2))/(r)=(1)/(4PI epsi_(0))(e^(2))/(r^(2))(Z=1)` `:.(mr^(2) omega^(2))/(r)=(1)/(4pi epsi_(0)) (e^(2))/(r^(2)) ( :. v=romega)` `:. m omega^(2)=(1)/(4pi epsi_(0))(e^(2))/(r^(3))` Here TAKING `omega=(2pi)/(T)`, `:.m((4pi^(2))/(T^(2)))=(1)/(4pi epsi_(0))(e^(2))/(r^(3))` `:.m=(e^(2)T^(2))/(16pi^(3)epsi_(0)r^(3))`

Discussion

45.	Hydrogen atom in ground state is excited by a monochromatic radiation of wavelength lambda = 975 Å then number of spectral lines in resulting spectrum emitted will be ......
Answer» 3 2 6 10 Solution :Energy of incident PHOTON, `E=hf=(hC)/(lambda)` `:.E=(6.625xx10^(-34)xx3xx10^(8))/(975xx10^(-10)xx1.6xx10^(-19))eV` `0.012746xx10^(3)` `=12.75eV` Now `E=-(13.6)/(N^(2))-(-(13.6)/(1^(2)))` `12.75=-(13.6)/(n^(2))+13.6` `:.(13.6)/(n^(2))=13.6-12.75` `:.(13.6)/(n^(2))=0.85eV` `:.n^(2)=(13.6)/(0.85)=16` `:. n=4` `:.` No, of spectral lines, `=(n(n-1))/(2)` `=(4(4-1))/(2)` `=6`

Discussion

46.	A beam of 30 MeV alpha particles is to be obtained from a cyclotron of radius 50cm . The strength of magnetic field required to be applied will be
Answer» 1.582 T 0.01582 T 0.1582 T 15.82 T Answer :A

Discussion

47.	Consider a uniformly charged hemispherical shell shown in figure. Indicate shown in figure. Indicate the directions (not magnitude) of the electric field at the central point P_1 and an off-center point P_2 on the drum-head of the shell.
Answer» `uparrow, ?` `uparrow,?` `uparrow,uparrow` `uparrow,larr` Solution :If ANOTHER shell is kept upside down over it complete a sphere, net field should BECOME ZERO.

Discussion

48.	The value of current I, in the figure shown will be
Answer» 11A 19 A 13 A 9A Answer :A

Discussion

49.	How do you convert a moving coil galvanometer into an ammeter?
Answer» SOLUTION :A moving COIL GALVANOMETER can be CONVERTED into ammeter by connecting a resistance in PARALLEL with the galvanometer.

Discussion

50.	What do you mean by fermi energy ?
Answer» Solution :The HIGHEST level OCCUPIED by the electrons at absolute ZERO is CALLED fermi level and the ENERGY corresponding to this level is called fermi energy

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A concave lens of focal length 20 cm is placed at a distance of 35 cm from an object. Find the position of the image and its magnification.

Calculate the value of I in the circuit given below.

the earth's atmosphere is richer in _____ radiations.

Two wires of the same material have their lengths in the ratio 3:2 , diameters in the ratio 3:2 and streching forces in the ratio 3:4 . What is the ratio of their extension

A second's pendulum is placed in a space laboratory orbitinground the earth at a heightof 3R, where Ris the radius of earth. The time period of the pendulum is :

The modern means of communication has this advantage of _____, _____ and possibility of _____ over a long distance.

The wavelength of Haline in hydrogen spectrum was found 6563 A^0 in the laboratory. If the wavelength of same line in the spectrum of a milky way is observed to be 6586 A^0, then the recessional velocity of the milky way will be

A circular coil of N-turns and of radius R is kept normal to a magnetic field given by B = B_(0) cos omegat. Deduce an expression for emf induced in this coil. State the rule which helps to detect the direction of induced current.

(A): An emf is induced in a closed loop where magnetic flux is varied. The induced electric field is not a conservative field (R): The line integral vecE.vec(dl) around the closed loop is non-zero

Liquid oxygen remains suspended between two pole faces of a strong horse shoe magnet because it is

Draw current v/s frequency curve for a series RLC circuit and explain the different portions of the curve.

The distnace between the diminished and the magnified images of slits for two position and d_1 and d_2 respectively. The distance between the virtual images of the slit is :

Refractive index of a thin convex lens is 1.5 and radii of curvature is 20 cm. The parallel rays incident on it intersect at distance .d., then d = ...... cm.

One coil with 40 turns and 4 "cm"^2 area of cross-section is kept perpendicular to one uniform magnetic field of flux density B. When this loop is pulled out of magnetic field suddenly, 2 xx 10^(-4) C electric charge flows through it. If resistance of this coil is 80Omega then B= ____ "Wb/m"^2.

There are two spheres of same mass and radius. One is solid and the other is hollow. Which of them has a larger moment of inertia about a diameter ?

In a Young double slit experiment, the width of the source slit is increased then……

A circular coil of N turns and radius R carries a current I. It is unwound and rewound to make another coil of radius R/2, current I remaining the same. Calculate the ratio of the magnetic moments of the new coil and the original coil.

What are the three chief uses of ‘studies’?

The plates of a parallel plate capacitor have area 2 m^2 each and are 10 cm. apart. If the charge on each plate is 8.85xx10^-12C, the electric field at a point:

A beam of radio active radiation is unaffected in a combined electric and magnetic field in mutually perpendicular direction. A boy argues that, it is essentially a gamma ray. Do you agree with him. Justify your answer.

How the self-inductance of a coil depends on number of turns in the coil ?

A n-p-n transistor conducts when

An em wave is propagating in a medium with a velocity vec(V)=V hat(i). The instantaneous oscillating electric field of this em waves is along + y axis. Then the direction of oscillating magnetic field of the em wave will be along

The width of spectral lines (spreading of spectral line) can be explained by -

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

A charge q_(0) is movedfrom point P to point q along the arc PQ with centre at O as shown in the figure near a long charged wire. The linear charge density of the wire is lambda and it in the same plane. Find the work done in the process.

Symbol Q stands for energy released

Compare the electrical conductivity of pure germanium at -40^(@)Cand+100^(@)C. The activation energy for germanium is 0.72 eV

If lower half of a concave mirror is blackned then

A : In interference, the fringe obtained at the centre of the screen is known as zeroth order fringe, or the central fringe R : In interference, path difference between the waves from S_(1)" and "S_(2), reaching the central fringe (or zero order fringe) is zero

A cell of emf epsilon and internal resistance (r) is connected in series with an external resistance (nr)then the ratio of the terminal potential difference to emf is:

A dices of mass M and radius R rolls without slipping on a leveled surface with a linear speed v. what is its kinetic energy?

(a) Determine the number of carbon ._6^(14)C atoms present for every gram of carbon ._6^(12)C in a living organism. Find (b) The decay constatnt and (c ) the activity of this sample.

A particle starts from the origin at t0s with a velocity of 10.0hatj m/s and moves in the X-y plane with a constant acceleration of (8hati +2hatj) ms^(-2). The y-coordinate of the particle in 2 sec is

In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole ?

A manometer connected to a closed tap reads 4.5 xx 10^5 Pa. When the tap is opened, the reading of the manometer falls to 4 × 10^5pascal. Then the velocity of flow of water is

Obtain the mass of an electron in hydrogen atom in terms of its orbital period and radius of orbit.

Hydrogen atom in ground state is excited by a monochromatic radiation of wavelength lambda = 975 Å then number of spectral lines in resulting spectrum emitted will be ......

A beam of 30 MeV alpha particles is to be obtained from a cyclotron of radius 50cm . The strength of magnetic field required to be applied will be

Consider a uniformly charged hemispherical shell shown in figure. Indicate shown in figure. Indicate the directions (not magnitude) of the electric field at the central point P_1 and an off-center point P_2 on the drum-head of the shell.

The value of current I, in the figure shown will be

How do you convert a moving coil galvanometer into an ammeter?

What do you mean by fermi energy ?

The modern means of communication has this advantage of ___, _ and possibility of ___ over a long distance.