physics objective upscprelims

8/6/2019 Physics Objective UPSCPrelims

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1. Work done when a force N acting on a particle takes it from the point

m to the point m is:(a) -3J(b) -1J(c) Zero

(d) 2JAns. (b)

2. The variation of momentum ith time of one of the bodies in a two-body collision is shown inthe given figure.

The instantaneous force is maximum corresponding to the point:(a) P(b) Q(c) R(d) SAns. (c)

3. A particle is subjected to two simple harmonic motionsx1=A1 sin t .

x2 = A2 sin (t + /4)The resultant simple harmonic motion will have an amplitude of:(a) (A1+A2)/2

Ans. (c)

4. A convex spherical surface made of glass of refractive index 1.62 having a radius of curvature5 cm is placed in air. The refraction matrix for this lens is:


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Ans. (a)

5. Work done in an isothermal expansion from volume V1 to volume V2 at temperature T is

given by:

Ans. (c)

6. The Clapeyrons equation L/(V2 V1) = T(P/T) V can be derived from:(a) (S/P) V = - (V/T) P(b) (CP/P) T = -T (

2V/T2) P(c) (S/V) T = (P/T) V(d) (P/V) T = - (P/T) V (T/V) PAns. (c)

7. Which one of the following curves represents Maxwells distribution law of velocities ofmolecules in a gas?

Ans. (d)


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8. The work done in moving an electron of charge and mass m from A to B along the circularpath. (shown by arrows in the given figure) in the vertical plane in the field of charge Q is:

(a) 2mgr(b) 2Qe/r(c) 2 mgr + 2Qe/r(d) ZeroAns. (d)

9. Two spheres of radii R1 and R2, joined by a line wire, are raised to a potential V. Let thesurface charge densities at these two spheres be, respectively

1and

2. Then:

(a) 2 = ( R1/R2)1(b) 2 = ( R2/R1)1(c) 2 = 1(d) 2 = ( R2/R1)

21Ans. (a)

10. Two particles A and B having equal charges are placed at distance d apart. A third chargedparticle, placed on the perpendicular bisector of AB at distance x1 will experience the maximumCoulomb force when:(a) x = d/2(b) x = d/2(c) x = d/22(d) x = d/32Ans. (c)

11. The given figure show two parallel planes A and B of charge densities +a and - a respectively

Electric intensity will be zero in the:

(a) Region I(b) Region II(c) Region III(d) Regions I and IIIAns. (d)


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12. Two identical capacitors A and B shown in the given circuit are joined in series with abattery. If a dielectric slab of dielectric constant K is slipped between the plates of capacitor Band battery remains connected, then theenergy of capacitor A will:

(a) Decrease(b) Increase(c) Remain the same(d) Be zero, since circuit will not work

Ans. (b)13. Four resistances each of 10 are connected as shown in given figure. The reading of theammeter A will be:

(a) 0.05 A(b) 0.2A(c) 0.4A(d) 0.8 AAns. (c)

14. A current of 2A flows in a system of conductors as shown in the given figure:

The potential difference VP VR will be:(a) - 2V(b) 1V(c) +1V(d) +2VAns. (c)


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15. In the arrangement shown in the given figure current from A to B is increasing in magnitude.Induced current in the loop will:

(a) Have clockwise direction(b) Have anticlockwise direction(c) Be zero(d) Oscillate between clockwise and anticlockwise directionsAns. (a)

16. In Rutherfords experiment on the scattering of a-particles by a metal foil, the scatteringcross-section depends on the angle of scattering, as:(a) sin4(/2)

(b) cosec4

(/2)(c) sin4(d) cosec4Ans. (b)

17. Match List-I with List-II and select the correct answer using the codes given below the lists:

Codes:

A B C D(a) 3 2 1 4(b) 3 4 2 1(c) 4 3 2 1(d) 2 3 1 4

Ans. (b)

18. In a photoelectric effect measurement the stopping potential for a given metal is found to beV0 volts when radiation of wavelength is used. If radiation of wavelength 2 is used with the samemetal, then the stopping potential will be observed to be (where symbols have their usualmeaning):(a) V0/2(b) 2V0


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(c) V0 + h/2e0(d) V0 + hc/2e0Ans. (d)

19. The half-life of214Bi is 20 mm. What fraction of a sample of 214Bi will remain after 2 h?

(a) 1/6(b) 1/20(c) 1/36(d) 1/64Ans. (d)

20. Which one of the following decays is permissible?(a) n p + - +(b) n p + + + v(c) p n + - +(d) p n + + + v

Ans. (a)

21. In the fusion process1

1H +21H

31H + e

+ + v + 4.6MeV,The types of interactions involved include:(a) Weak and strong(b) Weak and electromagnetic(c) Electromagnetic and strong(d) Weak, electromagnetic and strongAns. (b)

22. Consider the. Following elementary particles:1. p 2. 3. K0 4. +Of these the ones which belong to the baryon family include:(a) 1 and 2(b) 3 and 4(c) 2 and 3(d) 1, 2 and 4Ans. (d)

23. The voltage gain of a triode of amplification factor 7 and load resistance of 10 k is 10. Theplate resistance is(a) 5k(b) 7k(c) 10k(d) 15kAns. (a)


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24. The characteristic curve of an electronic device is shown in the given figure. To use thisdevice as an oscillator, the operating region should be between points.

(a) A and B(b) B and C(c) C and D(d) D and EAns. (b)

25. Match List I (I-V characteristics

) with List II (diodes

) and select the correct answer using

the codes given below the Lists:Codes:

A B C D


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(a) 4 2 3 1(b) 4 1 3 2(c) 3 2 4 1(d) 3 1 4 2Ans. (c)

26. Logic table given below shows the output for inputs A and B. The logic operation performedis:

(a) OR(b) XOR(c) NAND

(d) Negative of XORAns. (d)

27. The two binary inputs a and b are to be compared. The Boolean expression for the outputwhen a and b are equal is given by

(c) ab

Ans. (a)

28. The Boolean expression of the output Y in terms of the inputs A and B for the circuit shownin the following figure is:

Ans. (c)

29. A wheel of radius 1 m rolls forward half a revolution on a horizontal ground. The magnitudeof the displacement of the point of the wheel initially in contact with the ground is(a) 2(b) 2


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(c) (2 + 4 )(d) Ans. (a)

30. Two forces each of magnitude 2N, act at an angle of 600. The magnitude of the resultant

force is(a) l.l N(b) 4N(c)12N(d) 14.9NAns. (c)

31. An object moves along a straight line .path from P to Q under the action of a force,N. If the coordinates of P and, in meters, are (3, 2, - 1) and (2, -1, 4) respectively,

then the work done by the force is:(a) + 15J(b) -15J(c) 1015J

Ans. (a)

32. A particle is moving in a circular orbit of radius r1 with an angular velocity co. It jumps to

another circular orbit of radius r2 and attains an angular velocity If r2 = 0.5, and assuming thatno external torque is applied to the system, then, the angular velocity, (02 15 given by:(a) 2 = 41(b) 2 = 31(c) 2 = 21(d) 2 = 1Ans. (a)

33. If the linear density of a rod of length 3 m varies as = 2 + x, then the position of the centreof gravity of the rod is:

7 12(a) (7/3) m(b) (12/7) m(c) (10/7) m(d) (9/7) mAm. (b)


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34. The maximum velocity of a simple harmonic motion represented by y = 3 sin (100t + /6) isgiven by:(a) 300(b) 3/6(c) 100

(d) /6Ans. (a)

35. A simple pendulum of length L is set up inside a wagon sliding don a smooth inclined planeof inclination 0 with the horizontal. The period of oscillation recorded by an observer inside willbe:

Ans. (c)

36. A viscous fluid is flowing through a cylindrical tube. The velocity distribution of the fluid isthe best represented by the diagram:

Ans. (d)

37. Three simple harmonic oscillations, with amplitudes A1 > A2 > A3, pass through theirrespective equilibrium positions with the same velocity. If these oscillators have the same mass,then their characteristic frequencies and 3 will be related to each other as:


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Ans. (a)

38. Two simple harmonic waves of the same amplitude and frequency differ by a phase /2.

When they are fed simultaneously to the X-and Y-plates of a CRO, the screen would display thetrace of:(a) A circle(b) An ellipse(c) A straight line(d) A squareAns. (a)

39. The amplitude of the vibrating particle due to superposition of two SHMsy1 = sin (t + /2) andy2 = sin t is

(a) 1(b)2(c)3(d) 2Ans. (c)

40. A damped source of sound is set into vibration by an external force with a frequency .When is much larger than the natural frequency of the source, the average energy stored in thesource is:

(a) Mostly in the form of heat energy(b) Mostly in the form of potential energy(c) Mostly in the form of kinetic energy(d) Equally divided among kinetic and potential energiesAns. (a)

41. The thickness of a quarter- wave plate made of quartz for wavelength = 5000, refractiveindices e = 1.553 and t 0 = 1.543is:(a) 5.00 x 10-3cm(b) 3.75 x 10-3cm

(c) 2.50 x 10-3

cm(d) 1.25 x 10-3cmAns. (d)

42. A substance shows Raman frequency shift of 400 cm if this mode is active in the infrared,then the corresponding infrared absorption band will be at:(a) 0.5


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(b) 1.0(c) 1.5(d) 2.5Ans. (b)

43. Which one of the following Maxwells relations leads to Clausius-Clapeyron equation?(a) (T/V) S = - (P/S) V(b) (T/P) S = - (V/S) P(c) (V/T) P = - (S/P) P(d) (S/V) T = - (P/T) VAns. (d)

44. Which one of the 4ollowing statements regarding the electric fields and

is correct?(a) Both and can represent electrostatic field

(b) Neither nor can represent field(c) Only can represent electrostatic field(d) Only can represent electrostatic fieldAns. (c)

45. The equivalent capacitance of the given circuit is:

(a) 0.5 F(b) 1 F(c) 6.75 F(d) 9 FAns. (b)

46. 125 cm of potentiometer wire balances the emf of a cell and 100 cm of the wire is requiredfor balance if the poles of the cell are joined by a 2 resistor. The internal resistance of the cell is(a) 0.25 (b) 0.50 (c) 0.75

(d) 1.25 Ans. (b)

47. 200 accumulators are connected in series in two groups of 100 accumulators each, bothgroups being connected in parallel. The emf of each accumulator is 1.4 V and internal resistanceis 0.01 . The entire battery is connected through a rheostat to a dynamo generating 230 V. If thecharging current be 30 A, then the rheostat resistance is:(a) 0.1


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(b) 0.5 (c) 1.0 (d) 2.5 Ans. (c)

48. A conducting circular loop is placed in a uniform magnetic field of 0.02 T, with its planeperpendicular to the field. If the radius of the loop starts shrinking at a constant rate 1.0 mm/s.then the emf induced in the loop, at the instant when the radius is 4 cm, will be:(a) 2.0V(b) 2.5V(c) 5.0V(d) 8.0VAns. Cc)

49. In the resonate L-C-R series circuit shown in the figure if we change the value of R, it will:

(a) Not affect the voltages across the individual components L, C and R(b) Affect that voltage across R but not across L or C(c) Not affect the voltage across R(d) No affect the voltage across the LC combination but will affect the, voltage across RAns. (b)

50. The torque required to hold a small circular coil of 10 turns, 2 x 10-4 m2 area and carrying 0.5A current in the middle of a long solenoid of 10 -3 turns/m carrying 3 A current, with its axisperpendicular to the axis of the solenoid, is(a) 12 x 10-7 N-m(b) 6 x 10-7 N-m(c) 4 x 10-7 N-m(d) 2 x 10-7 N-mAns. (a)

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