Electromagnetic Waves — Physics STD 12 Science — Question

A wire has resistance 12 Ω. It is bent in the form of a circle. The effective resistance between the two points on any diameter is equal to

(a) 12 Ω

(b) 6 Ω

(c) 3 Ω

(d) 24 Ω

A plane electromagnetic wave is incident on a material surface. If the wave delivers momentum p and energy E, then

(a) p = 0, E = 0

(b) p ¹ 0, E ¹ 0

(c) p ¹ 0, E = 0

(d) p = 0, E ¹ 0

A long, straight wire of radius R carries a current distributed uniformly over its cross section. T he magnitude of the magnetic field is:

1. Maximum at the axis of the wire.
2. Minimum at the axis of the wire.
3. Maximum at the surface of the wire.
4. Minimum at the surface of the wire.

Two different metals are joined end to end. One end is kept at constant temperature and the other end is heated to a very high temperature. The graph depicting the thermo e.m.f. is

(a)

(b)

(c)

(d)

While doing his experiment, Millikan one day observed the following charges on a single drop

(i) 6.563   (ii) 8.204   (iii) 11.50   (iv) 13.13   (v) 16.48   (vi) 18.09

From this data the value of the elementary charge (e) was found to be

(a) 1.641

(b) 1.630

(c) 1.648

(d) 1.602

When two identical capacitors are in series have 3mF  capacitance and when parallel 12mF. What is the capacitance of each

(a) 6 μF

(b) 3 μF

(c) 12 μF

(d) 9 μF

The conductivity of a superconductor is

(a) Infinite

(b) Very large

(c) Very small

(d) Zero

16 gm sample of a radioactive element is taken from Bombay to Delhi in 2 hour and it was found that 1 gm of the element remained (undisintegrated). Half life of the element is

(a) 2 hour

(b) 1 hour

(c)

(d)

An A.C. circuit containing only capacitance, the current:

According to de-Broglie, the de-Broglie wavelength for electron in an orbit of hydrogen atom is 10^–9 m. The principle quantum number for this electron is

(a) 1

(b) 2

(c) 3

(d) 4