Current Electricity — Physics STD 12 Science — Question

The voltage gain of the following amplifier is

(a) 10

(b) 100

(c) 1000

(d) 9.9

The magnetic compass is not useful for navigation near the magnetic poles because

(a) The magnetic field near the poles is zero

(b) The magnetic field near the poles is almost vertical

(c) At low temperature, the compass needle looses its magnetic properties

(d) Neither of the above

A metal plate gets heated, when cathode rays strike against, it due to

(a) Kinetic energy of cathode rays	(b) Potential energy of cathode rays
(c) Linear velocity of cathode rays	(d) Angular velocity of cathode rays

For a fast chain reaction, the size of U²³⁵ block, as compared to its critical size, must be:

The measurement of voltmeter in the following circuit is

(a) 2.4 V

(b) 3.4 V

(c) 4.0 V

(d) 6.0 V

The minimum heat energy required to emit an electron from the surface of a metal is called _________:

In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was fraction equal to

(a) 1 / 8

(b) 1 / 6

(c) 1 / 10

(d) 1 / 4

Two parallel slits 0.6 mm apart are illuminated by light source of wavelength 6000 Å. The distance between two consecutive dark fringes on a screen 1 m away from the slits is

(a) 1 mm

(b) 0.01 mm

(c) 0.1 m

(d) 10 m

In order to pass 10% of main current through a moving coil galvanometer of 99 ohm, the resistance of the required shunt is

(a) 9.9 Ω

(b) 10 Ω

(c) 11 Ω

(d) 9 Ω

The magnetic field of the earth can be modelled by that of a point dipole placed at the centre of the earth. The dipole axis makes an angle of 11.3° with the axis of the earth. At Mumbai, declination is nearly zero. Then,