Electric Charges and Fields — Physics STD 12 Science — Question

Number of electric lines of force emanating from 1C of positive charge in vacuum is:

If flux of the electric field through a closed surface is zero:

1. The electric field must be zero everywhere on the surface.
2. The electric field may be zero everywhere in the surface.
3. The charge inside the surface must be zero.
4. The charge in the vicinity of the surface must be zero.

Sodium has body centred packing. If the distance between two nearest atoms is 3.7 Å, then its lattice parameter is

(a) 4.8 Å

(b) 4.3 Å

(c) 3.9 Å

(d) 3.3 Å

Two files lines can ____.

Let p and E denote the linear momentum and energy of a photon. If the wavelength is decreased:

1. Both p and E increase.
2. P increases and E decreases.
3. P decreases and E increases.
4. Both p and E decrease.

Binding energy of a nucleus is of the order of.

A wire of diameter 0.02 metre contains 10²⁸ free electrons per cubic metre. For an electrical current of 100 A, the drift velocity of the free electrons in the wire is nearly

(a) 1 × 10–19 m/s

(b) 5 × 10–10 m/s

(c) 2 × 10–4 m/s

(d) 8 ×103 m/s

A semi conductor device with both active and passive electronic elements diffused into a silicon water to form a functional circuit is called.

In which of the following systems will the radius of the first orbit (n = 1) be minimum?

The specific resistance of a rod of copper as compared to that of thin wire of copper is: