Nuclei — Physics STD 12 Science — Question

In Fig, Vo is the potential barrier across a p-n junction, when no battery is connected across the junction:

When a ferromagnetic material goes through a hysteresis loop, the magnetic susceptibility:

1. Has a fixed value.
2. May be zero.
3. May be infinity.
4. May be negative.

Beyond which frequency, the ionosphere bands any incident electromagnetic radiation but do not reflect it back towards the earth?

Electric field lines cannot forms the:

The introduction of a grid in a triode valve affects plate current by

(a) Making the thermionic emission easier at low temperature

(b) Releasing more electrons from the plate

(c) By increasing plate voltage

(d) By neutralising space charge

The principle of controlled chain reaction is used in

(a) Atomic energy reactor	(b) Atom bomb
(c) The core of sun	(d) Artificial radioactivity

Wavenumber of radiations having frequency of 4×10¹⁴Hz will be:

If a current increases from zero to one ampere in 0.1 second in a coil of 5mH, then the magnitude of the induced e.m.f. will be.

The condition for a uniform spherical mass m of radius r to be a black hole is [G = gravitational constant and g = acceleration due to gravity]

(a)

(b)

(c)

(d)