Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Monochromatic green light of wavelength 5  illuminates a pair of slits 1 mm apart. The separation of bright lines on the interference pattern formed on a screen 2 m away is

(a) 0.25 mm

(b) 0.1 mm

(c) 1.0 mm

(d) 0.01 mm

An electric dipole is placed at the centre of a sphere.
Mark the correct options:

1. The flux of the electric field through the sphere is zero.
2. The electric field is zero at every point of the sphere.
3. The electric field is not zero anywhere on the sphere.
4. The electric field is zero on a circle on the sphere.

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)

In double slits experiment, for light of which colour the fringe width will be minimum

(a) Violet

(b) Red

(c) Green

(d) Yellow

In the circuit shown in figure, the current drawn from the battery is 4A.  If 10 W resistor is replaced by 20 W resistor, then current drawn from the circuit will be

(a) 1 A

(b) 2 A

(c) 3 A

(d) 0 A

In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was fraction equal to

(a) 1 / 8

(b) 1 / 6

(c) 1 / 10

(d) 1 / 4

Two identical coaxial circular loops carry current i each circulating in the clockwise direction. If the loops are approaching each other, then             

(a) Current in each loop increases

(b) Current in each loop remains the same

(c) Current in each loop decreases

(d) Current in one-loop increases and in the other it decreases

The amplification factor of a triode valve is 15. If the grid voltage is changed by 0.3 volt the change in plate voltage in order to keep the plate current constant (in volt) is

(a) 0.02

(b) 0.002

(c) 4.5

(d) 5.0

Energy released in fusion of 1 kg of deuterium nuclei

(a) 8

(b) 6

(c) 2

(d) 8

When a glass rod is rubbed with silk, it

(a) Gains electrons from silk	(b) Gives electrons to silk
(c) Gains protons from silk	(d) Gives protons to silk