1.     In nature, the electric charge of any system is always–

        Ans:    Quantisation of charge

                    Choice (D)

2.     The energy stored in the capacitor as shown in   Fig. (a) is 4.5 ´ 10^{- 6} J. If the battery is replaced     by –

        Ans:   

                    = 4.5 ´ 10^{- 6} J

                   Choice (B)

3.     Equal amounts of a metal are converted into        cylindrical wires of different lengths (L) and cross-sectional –

        Ans:    R =

                   Choice (C)

4.     If the force exerted by an electric dipole on a         charge q at a distance of 1 m is F, the force–

        Ans:   

                    Choice (D)

5.     A solid sphere of radius R ₁ and volume charge   density r = is enclosed by a hollow sphere of        radius R₂ with negative surface charge density–

        Ans:    Q _in =

                    =

                    = 4p R₂²s

                    Choice (C)

6.     A solid spherical conductor of radius R has a      spherical cavity of radius a9a < R) at its centre. A        charge +Q is kept at the center.–

        Ans:

                Choice (B)

7.     A cylindrical capacitor has charge Q and length L. If both –

        Ans:    U ₁ =

                    U ₂ =

        Choice (B)

8.     Three resistances of 4 W each are connected as shown in figure. If the point D divides the resistance –

        Ans:   

        Choice (C)

9.     The resistance of a metal increases with increasing –

        Ans:    Vibration of lattice ions increases with                                  

                    temperature

        Choice (B)

10.  In the absence of applied potential, the electric current flowing through-

        Ans:    Thermal velocity of electrons is in random                           

                    directions

        Choice (C)

11.  A meter bridge is used to determine the resistance of an unknown wire by measuring the balance point length l. If the wire is replaced by –

        Ans:   

12.  Identify the INCORRECT statement regarding –

        Ans:    Supercurrent always flows on the surface                            

                    of the superconductor

        Choice (B)

13.  A sample of HCl gas is placed in an electric field of 3 ´ 10⁴ NC^{- 1}. The dipole moment of each HCl molecule is –

        Ans:    t = pE

        Choice (C)

14.  When a metallic plate swings between the  –

        Ans:    Lenz’s law

        Choice (C)

15.  When an electrical appliance is switched on, it responds almost-

        Ans:    Electromagnetic waves travel with the                                   

                    speed of light

                    Choice (B)

16.  Two identical incandescent light bulbs are connected as shown in the figure. When the circuit is an AC voltage source–

        Ans:    At resonance X_L = X_C

                    Choice (B)

17.  A transformer rated at 10 kW is used to connect a 5 kV transmission line to a 240 V circuit. The ratio –

        Ans:    n =

                    Choice (B)

18.  Three solenoid coils of same dimension, same number of turns and same number of layers of winding are taken. Coil 1 with inductance L₁ was wound using a Mn wire of resistance 11 W / m; –

        Ans:    Alternate winding in opposite direction                                  

                    total flux = 0

                    Choice (C)

19.  Light travels with a speed of 2 ´ 10⁸ m/s in crown glass of refractive index 1.5. What is the speed of light –

        Ans:    n ₁v₁ = n₂v₂

                    Choice (B)

20.  A parallel beam of fast moving electrons is incident normally on a narrow slit. A screen is placed at a large distance from the slit.–

        Ans:    sinq =

                    Choice (C)

21.  Two beams of light will not give rise to an –

        Ans:    Since the polarization vectors are                                           

                    perpendicular their vector sum ¹ 0

                    Choice (C)

22.  A slit of width `a’ is illuminated with a monochromatic light of wavelength l from a distant source and the diffraction pattern –

        Ans:    sinq =

                    Choice (B)

23.  A thin film of soap solution (n = 1.4) lies on the top of a glass plate (n = 1.5). When visible light is incident almost normal to the plate, two adjacent reflection –

        Ans:    n ₁l ₁ = n₂l ₂

                    2n ₁ = 3n₂

                    Þ n₁ = 3

                    d = = 450

                    Choice (B)

24.  If the speed of a wave doubles as it passes from shallow water into deeper water, –

        Ans:    c = fl

                    Choice (C)

25.  A light whose frequency is equal to 6 ´ 10¹⁴ Hz is incident on a metal whose work function is

2 eV –

        Ans:    hu = f + K.E

                    Choice (C)

26.  An electron microscope is used to probe the atomic arrangements to a resolution of . What should be the electric potential –

        Ans:   

                    Choice (D)

27.  Which phenomenon best supports the theory that matter –

        Ans:    Electrons behave also as waves of l =

                    Choice (B)

28.  The radioactivity of a certain material drops to of the initial value in 2 hours. The half –

        Ans:    Activity changes from A₀ to A₀/16 implies 4                             half-lives.

                    Choice (C)

29.  An observer `A’ sees an asteroid with a radioactive element moving by at a speed = 0.3 c and measures the radioactivity decay time to be T<sub>A</sub>. Another observer `B’ –

        Ans:    Moving clocks are slower T_B < T_A

                    Choice (A)

30.  ²³⁴U has 92 protons and 234 nucleons total in its nucleus. It decays by emitting an alpha –

        Ans:    ²³⁴U₉₂ à ²³⁰Th₉₀ + a

                    Choice (C)

31.  K_a and K_b x-rays are emitted when there is a transition of electron –

        Ans:    K series end in n = 1

                    Choice (A)

32.  A certain radioactive material _ZX^A starts emitting a and b particles successively such that the end product –

        Ans:    _ZX^A à _{Z- 3}Y^{A- 8} + 2a + 1b

                    Choice (B)

33.  In the circuit shown above, an input of 1 V is fed into the inverting input of an ideal Op-amp A. The output signal –

        Ans:    = - 10 (negative feedback)

                    Choice (B)

34.  When a solid with a band gap has a donor level just below its empty energy band, -

        Ans:    Knowledge based

                    Choice (D)

35.  A p – n junction has acceptor impurity concentration of 10¹⁷ cm^{- 3} in the P side and donor impurity concentration of 10¹⁶ cm^{- 3} in the N side. What is the contact potential at the –

        Ans:    V _contact =

                    Choice (A)

36.  A zener diode has a contact potential of 1 V in the absence of biasing. It undergoes zener breakdown for an electric field of 10⁶ V/m at the depletion region of p-n junction. If the width –

        Ans:    V = Ed

                    Choice (B)

37.  In Colpitt oscillator the feedback network –

        Ans:    a-c equivalent circuit.

                    Choice (B)

38.  The reverse saturation of p-n diode

        Ans:    Knowledge based

                    Choice (D)

39.  A radio station has two channels. One is AM at 1020 kHz and the other FM at 89.5 MHz. –

        Ans:    Knowledge based

                    Choice (A)

40.  The communication using optical fibers is –

        Ans:    Optic fibre uses T.I.R.

                    Choice (A)