Moving Charges and Magnetism — Physics STD 12 Science — Question

In the following transitions, which one has higher frequency

(a) 3 – 2

(b) 4 – 3

(c) 4 – 2

(d) 3 – 1

Magnitude of magnetic field for a definite cross-section of a current carrying toroid is:

Curie is a unit of

(a) Length

(b) It is not any unit

(c) Activity

(d) Atomic number

A moderator is used in nuclear reactors in order to:

Consider two waves passing through the same string. Principle of superposition for displacement says that the net displacement of a particle on the string is sum of the displacements produced by the two waves individually. Suppose we state similar principles for the net velocity of the particle and the net kinetic energy of the particle. Such a principle will be valid for:

1. Both the velocity and the kinetic energy.
2. The velocity but not for the kinetic energy.
3. The kinetic energy but not for the velocity.
4. Neither the velocity nor the kinetic energy.

The drift current in a p-n junction is from the:

Assertion :   Magnetic field interacts with a moving charge and not with a stationary charge.

Reason    : A moving charge produces a magnetic field.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Constantan wire is used for making standard resistance, because it has:

A photodetector is made from a semiconductor In _0.53Ga _0.47As with E_g = 0.73 eV. What is the maximum wavelength, which it can detect

(a) 1000 nm

(b) 1703 nm

(c) 500 nm

(d) 173 nm

A charge q coulomb moves in a circle at n revolutions per second and the radius of the circle is r metre. Then magnetic field at the centre of the circle is

(a)  N/amp/metre	(b)  N/amp/metre
(c) N/amp/metre	(d)  N/amp/metre