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

An A.C. source is connected to a resistive circuit. Which of the following is true?

A test charge is moved from lower potential point to a higher potential point. The potential energy of test charge will ______.

An electric dipole of moment `vec"p"` is placed in a uniform electric field `vec"E"`. Then ______.

1. the torque on the dipole is `vec"p" xx vex"E"`
2. the potential energy of the system is `vec"p" * vec"E"`
3. the resultant force on the dipole is zero.

Choose the correct option.

If a conductor has a potential V ≠ 0 and there are no charges anywhere else outside, then ______.

Magnetic moment for solenoid and corresponding bar magnet is ______.

Name the e.m. waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.

If the Earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.

An e.m. wave exerts pressure on the surface on which it is incident. Justify.

If a conductor has a potential V ≠ 0 and there are no charges anywhere else outside, then ______.

1. there must be charges on the surface or inside itself.
2. there cannot be any charge in the body of the conductor.
3. there must be charges only on the surface.
4. there must be charges inside the surface.

A toroid of n turns, mean radius R and cross-sectional radius a carries current I. It is placed on a horizontal table taken as x-y plane. Its magnetic moment m ______.

A proton has spin and magnetic moment just like an electron. Why then its effect is neglected in magnetism of materials?

A ball of superconducting material is dipped in liquid nitrogen and placed near a bar magnet. (i) In which direction will it move? (ii) What will be the direction of it’s magnetic moment?

Suppose we want to verify the analogy between electrostatic and magnetostatic by an explicit experiment. Consider the motion of (i) electric dipole p in an electrostatic field E and (ii) magnetic dipole m in a magnetic field B. Write down a set of conditions on E, B, p, m so that the two motions are verified to be identical. (Assume identical initial conditions.)

A bar magnet of magnetic moment m and moment of inertia I (about centre, perpendicular to length) is cut into two equal pieces, perpendicular to length. Let T be the period of oscillations of the original magnet about an axis through the midpoint, perpendicular to length, in a magnetic field B. What would be the similar period T′ for each piece?

Use (i) the Ampere’s law for H and (ii) continuity of lines of B, to conclude that inside a bar magnet, (a) lines of H run from the N pole to S pole, while (b) lines of B must run from the S pole to N pole.

Verify the Ampere’s law for magnetic field of a point dipole of dipole moment m = m`hatk`. Take C as the closed curve running clockwise along (i) the z-axis from z = a > 0 to z = R; (ii) along the quarter circle of radius R and centre at the origin, in the first quadrant of x-z plane; (iii) along the x-axis from x = R to x = a, and (iv) along the quarter circle of radius a and centre at the origin in the first quadrant of x-z plane.