Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Two identical blocks are kept on a frictionless horizontal table connected by a spring of stiffness k and of original length l₀. A total charge Q is distributed on the block such that maximum elongation of spring at equilibrium is equal to x. Value of Q is ______.

Assertion: Electric field is discontinuous across the surface of a spherical charged shell.
Reason: Electric potential is continuous across the surface of a spherical charged shell.

Consider the following statements and select the correct statement(s).

1. Electric field lines are always perpendicular to equipotential surface.
2. No two equipotential surfaces can intersect each other.
3. Electric field lines are in the direction of tangent to an equipotential surface.

Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately.

The diagrams below show regions of equipotentials.

(i)	(ii)
(iii)	(iv)

A positive charge is moved from A to B in each diagram.

1. The potential at all the points on an equipotential surface is same.
2. Equipotential surfaces never intersect each other.
3. Work done in moving a charge from one point to other on an equipotential surface is zero.

A charged particle moves through a magnetic field perpendicular to its direction. Then ______.

1. The presence of a large magnetic flux through a coil maintains a current in the coil if the circuit is continuous.
2. A coil of a metal wire kept stationary in a non– uniform magnetic field has an e.m.f induced in it.
3. A charged particle enters a region of uniform magnetic field at an angle of 85° to the magnetic lines of force, the path of the particle is a circle.
4. There is no change in the energy of a charged particle moving in a magnetic field although a magnetic force is acting on it.

The given figure represents a material which is ______.

Assertion: The ferromagnetic substance do not obey Curie’s law.
Reason: At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.

The coercivity of a small magnet where the ferromagnet gets demagnetized is 3 × 10³ Am^–1. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is ______.

Assertion: A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled.
Reason: The magnetisation does not depend on temperature.

The magnetic susceptibility is negative for ______.