Electric Charges and Fields — Physics STD 12 Science — Question

Peltier coefficient for the junction of a pair of metals is proportional to

(a) T absolute temperature of the junction

(b) Square of absolute temperature of the junction

(c)

(d)

A toroid has number of turns per unit length n, current i, then the magnetic field is

(a)

(b)

(c)

(d) None of these

If the frequency of light in a photoelectric experiment is doubled, the stopping potential will:

A piece of wood is floating in water kept in a bottle. The bottle is connected to an air pump. Neglect the compressibility of water. When more air is pushed into the bottle from the pump, the piece of wood will float with.

1. Larger part in the water.
2. Lesser part in the water.
3. Same part in the water.
4. It will sink.

The electric potential at a point on the axis of an electric dipole depends on the distance r of the point from the dipole as

(a) ∝

(b) ∝

(c) ∝ r

(d) ∝

A charge q is located at the centre of a cube. The electric flux through any face is

(a)

(b)

(c)

(d)

The time period of oscillation of a magnet in a vibration magnetometer is 1.5 seconds. The time period of oscillation of another magnet similar in size, shape and mass but having one-fourth magnetic moment than that of first magnet, oscillating at same place will be

(a) 0.75 sec

(b) 1.5 sec

(c) 3 sec

(d) 6 sec

The direction of induced e.m.f. during electromagnetic induction is given by

(a) Faraday's law

(b) Lenz's law

(c) Maxwell's law

(d) Ampere's law

If a diamagnetic substance is brought near north or south pole of a bar magnet, it is

(a) Attracted by the poles

(b) Repelled by the poles

(c) Repelled by the north pole and attracted by the south pole

(d) Attracted by the north pole and repelled by the south pole

Which source is associated with a line emission spectrum?