Alternating Current — Physics STD 12 Science — Question

An electron and a proton are both released from rest 1 meter from a large stationary negative charge, considering only the force from the large stationary negative charge on the proton and electron. Which of the following is true?

In a semiconductor:

1. There are no free electrons at 0K.
2. There are no free electrons at any temperature.
3. The number of free electrons increases with temperature.
4. The number of free electrons is less than that in a conductor.

Identify the correct statement from the following.

If n, e, τ and m respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length l  and area of cross-section  A will be

(a)

(b)

(c)

(d)

Human eye:

If a charged spherical conductor of radius 10 cm has potential V at a point distant 5 cm from its centre, then the potential at a point distant 15 cm  from the centre will be

(a)

(b)

(c)

(d) 3V

An AC source is rated 220V, 50Hz. The average voltage is calculated in a time interval of 0.01s, It:

Which of the following is constructed on the principle of electromagnetic induction

(a)  Galvanometer

(b) Electric motor

(c)  Generator

(d) Voltmeter

The figure shows some of the electric field lines corresponding to an electric field. The figure suggests

(a)

(b)

(c)

(d)

In cyclotron the gyro radius is: