Electric Charges and Fields — Physics STD 12 Science — Question

A square loop of side l is moving with a constant velocity v in a uniform magnetic field. The magnitude of induced emf is:

For a given value of n, the number of electrons in an orbit is?

Radio waves and visible light in vacuum have

(a) Same velocity but different wavelength

(b) Continuous emission spectrum

(c) Band absorption spectrum

(d) Line emission spectrum

According to photon theory of light which of the following physical quantities associated with a photon do not/does not change as it collides with an electron in vacuum

(a) Energy and momentum	(b) Speed and momentum
(c) Speed only	(d) Energy only

The magnetic dipole moment of a current carrying coil does not depend upon:

A current of 1 ampere is passed through a straight wire of length 2.0 metres. The magnetic field at a point in air at a distance of 3 metres from either end of wire and lying on the axis of wire will be

(a)

(b)

(c)

(d) Zero

The turn ratio of a transformers is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through load resistance

(a) 1 A

(b) 4.5 A

(c) 2 A

(d) 1. 5 A

Let V and E represent the gravitational potential and field at a distance r from the centre of a uniform solid sphere. Consider the two statements:

1. The plot of V against r is discontinuous.
2. The plot of E against r is discontinuous.

1. Both A and B are correct.
2. A is correct but B is wrong.
3. B is correct but A is wrong.
4. Both A and B are wrong.