Moving Charges and Magnetism — Physics STD 12 Science — Question

A man runs towards mirror at a speed of 15 m/s. What is the speed of his image

(a) 7.5 m/s

(b) 15 m/s

(c) 30 m/s

(d) 45 m/s

+q, +2q, +3q, +4q, ……(up to +20q) charges are situated at coordinates (0, 0), (1, 0), (2, 0), ….. (Up to 20). What is the total charge stored in the system?

According to Bohr's theory, the electron in orbits have definite energy values, then according to uncertainty principle, the life time of an excited state will be:

Study involving both electricity and magnetism is called ______.

The curie weiss law is obeyed by iron:

Rate of change of torque τ with deflection θ is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when

(a) θ = 0°

(b) θ = 45°

(c) θ = 60°

(d) θ = 90°

Three observers A, B and C measure the speed of light coming from a source to be  and . The observer A moves towards the source, the observer C moves away from the source with the same speed. The observer B stays stationary. the surrounding space is vacuum every where. Then

(a)

(b)

(c)

(d)

Assertion :   The properties of paramagnetic and ferromagnetic substance are not effected by heating.

Reason     : As temperature rises, the alignment of molecular magnets gradually decreases.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

The electric potential V at any point O (x, y, z all in metres) in space is given by . The electric field at the point (1m,0, 2m)  in volt/metre  is

(a) 8 along negative X - axis	(b) 8 along positive X -  axis
(c) 16 along negative X -  axis	(d) 16 along positive Z - axis