Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Physics

On the basis of the graphs shown in the figure, answer the following questions :

(a) Which physical parameter is kept constant for the three curves?

(b) Which is the highest frequency among v₁, v_2, and v₃?

Write two distinguishing features of nuclear forces.

Identify the following magnetic materials :

Define the terms "stopping potential' and 'threshold frequency' in relation to the photoelectric effect. How does one determine these physical quantities using Einstein's equation?

Explain, with the help of a suitable example, how we can show that Lenz's law is a consequence of the principle of conservation of energy.

Depict the equipotential surface due to
(i) an electric dipole,
(ii) two identical positive charges separated by a distance.

In the case of photoelectric effect experiment, explain the following facts, giving reasons.
The photoelectric current increases with increase of intensity of incident light.

Write two important characteristics of equipotential surfaces.

Define the term: stopping potential in the photoelectric effect.

The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?

A short bar magnet has a magnetic moment of 0.48 J T⁻¹. Give the direction and magnitude of the magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on

1. the axis,
2. the equatorial lines (normal bisector) of the magnet.

Suppose the initial charge on the capacitor is 6 mC. What is the total energy stored in the circuit initially? What is the total energy at later time?

A magnetic field that varies in magnitude from point to point but has a constant direction (east to west) is set up in a chamber. A charged particle enters the chamber and travels undeflected along a straight path with constant speed. What can you say about the initial velocity of the particle?

Why does a paramagnetic sample display greater magnetisation (for the same magnetising field) when cooled?

Why is diamagnetism, in contrast, almost independent of temperature?

If a toroid uses bismuth for its core, will the field in the core be (slightly) greater or (slightly) less than when the core is empty?

Is the permeability of a ferromagnetic material independent of the magnetic field? If not, is it more for lower or higher fields?

Magnetic field lines are always nearly normal to the surface of a ferromagnet at every point. (This fact is analogous to the static electric field lines being normal to the surface of a conductor at every point.) Why?

Would the maximum possible magnetisation of a paramagnetic sample be of the same order of magnitude as the magnetisation of a ferromagnet?

Explain qualitatively on the basis of domain picture the irreversibility in the magnetisation curve of a ferromagnet.