Nuclei — Physics STD 12 Science — Question

Retina of eye acts like ........ of camera

(a) Shutter

(b) Film

(c) Lens

(d) None of these

The frequencies of X-rays, g-rays and ultraviolet rays are respectively a, b and c. Then

(a) a < b, b > c

(b) a > b, b > c

(c) a > b, b < c

(d) a < b, b < c

The capacity of a condenser in which a dielectric of dielectric constant 5 has been used, is  C. If the dielectric is replaced by another with dielectric constant 20, the capacity will become

(a)

(b) 4C

(c)

(d) 2C

20 μA current flows for 30 seconds in a wire, transfer of charge will be

(a) 2

(b) 4

(c) 6

(d) 8

A potentiometer having the potential gradient of 2 mV/cm is used to measure the difference of potential across a resistance of 10 ohm. If a length of 50 cm of the potentiometer wire is required to get the null point, the current passing through the 10 ohm resistor is (in mA)

(a) 1

(b) 2

(c) 5

(d) 10

The state of photo-electrons emerging from the metal surface can be :

What is the C.G.S. unit of charge?

Two metal plates having charges Q, -Q face each other at some separation and are dipped into an oil tank. If the oil is pumped out, the electric field between the plates will:

1. Increase.
2. Decrease.
3. Remain the same.
4. Become zero.

A charge of 5 C  is given a displacement of 0.5 m. The work done in the process is 10 J. The potential difference between the two points will be

(a) 2 V

(b) 0.25 V

(c) 1V

(d) 25 V