Permanent Magnets — Physics STD 12 Science — Question

How does the electric flux due to a point charge enclosed by a spherical Gaussian surface get affected when its radius is increased?

What is the magnitude of electromotive forces of batteries used in any closed electric circuit?

How the direction of induced electromotive force is determined?

Why a core of soft iron is used in a moving coil galvanometer?

Name the part of electromagnetic spectrum which is used for taking photographs of earth under foggy conditions from great heights.

NaCl molecule is bound due to the electric force between the sodium and the chlorine ions when one electron. of sodium is transferred to chlorine. Taking the separation between the ions to be 2.75 × 10cm, find the force of attraction between them· State the assumptions (if any) that you have made.

Does the stopping potential in photoelectric emission depend upon,

1. The intensity of the incident radiation in a photocell?
2. The frequency of the incident radiation?

When a semiconducting material is doped with an impurity, new acceptor levels are created. In a particular thermal collision, a valence electron receives an energy equal to 2kT and just reaches one of the acceptor levels. Assuming that the energy of the electron was at the top edge of the valence band and that the temperature T is equal to 300K, find the energy of the acceptor levels above the valence band.

A glass lens of refractive index 1.5 is placed in a trough of liquid. What must be the refractive index of the liquid in order to make the lens disappear?

Write the following radiations in ascending order in respect of their frequencies: X-rays, microwaves, UV rays and radio waves.