Atoms — Physics STD 12 Science — Question

Which of the following is responsible for the earth’s magnetic field?

Which one of the following is the weakest kind of bonding in solids

(a) Ionic

(b) Metallic

(c) Vander Waals

(d) Covalent

Photoelectric effect supports quantum nature of light because:

1. There is a minimum frequency below which no photoelectrons are emitted.
2. The maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity.
3. Even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately.
4. Electric charge of the photoelectrons is quantized.

A p-n junction diode cannot be used:

Current through wire XY of circuit shown is

(a) 1 A

(b) 4 A

(c) 2 A

(d) 3 A

Which metal is used to make ferromagnets ?

Basically, the product modulator is

(a) An amplifier	(b) A mixer
(c) A frequency separator	(d) A phase separator

A magnet of magnetic moment M oscillating freely in earth's horizontal magnetic field makes n oscillations per minute. If the magnetic moment is quadrupled and the earth's field is doubled, the number of oscillations made per minute would be

(a)

(b)

(c) 2

(d)

The work done by the external forces on a system equals the change in:

1. Total energy.
2. Kinetic energy.
3. Potential energy.
4. None of these.

In cyclotron the gyro radius is: