Electric Charges and Fields — Physics STD 12 Science — Question

The sensitivity of a tangent galvanometer is increased if

(a) Number of turn decreases	(b) Number of turn increases
(c) Field increases	(d) None of the above

A plane electromagnetic wave propagating along x direction can have the following pairs of E and B.

Energy required to remove an electron from aluminium surface is 4.2 eV. If light of wavelength 2000 Å falls on the surface, the velocity of the fastest electron ejected from the surface will be

(a) 8.4

(b) 7.4

(c) 6.4

(d) 8.4

When a compact disc is illuminated by a source of white light. Coloured 'lanes' are observed. This is due to

(a) Dispersion

(b) Diffraction

(c) Interference

(d) Refraction

Gases exert pressure on the walls of the container, because the gas molecules:

Plane of eddy currents makes an angle with the plane of magnetic lines of force equal to

(a) 40°

(b) 0°

(c) 90°

(d) 180°

A particle moves with a constant velocity parallel to the X-axis. Its angular momentum with respect to the origin:

1. Is zero.
2. Remains constant.
3. Goes on Increasing.
4. Goes on decreasing.

In Cu-Fe couple, the flow of current at the temperature of inversion is

(a) From Fe to Cu through the hot junction

(b) From Cu to Fe through the hot junction

(c) Maximum

(d) None of the above

Constantan wire is used in making standard resistances because its

(a) Specific resistance is low

(b) Density is high

(c) Temperature coefficient of resistance is negligible

(d) Melting point is high