Electric Charges and Fields — Physics STD 12 Science — Question

Photoelectric effect proves that light wave :

Lens used to remove long sightedness (hypermetropia) is

(a) Concave lens	(b) Plano-concave lens
(c) Convexo-concave lens	(d) Convex lens

Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?

A magnetic needle is made to vibrate in uniform field H, then its time period is T. If it vibrates in the field of intensity 4H, its time period will be

(a) 2T

(b) T/2

(c) 2/T

(c) 2/T

When light rays are incident on a prism at an angle of 45°, the minimum deviation is obtained. If refractive index of the material of prism is , then the angle of prism will be

(a) 30°

(b) 40°

(c) 50°

(d) 60°

What is ozone hole

(a) Hole in the ozone layer

(b) Formation of ozone layer

(c) Thinning of ozone layer in troposphere

(d) Reduction in ozone thickness in stratosphere

The length of side of a square coil is 50cm and number of turns in it is 100. If it is placed at right angles to a magnetic field which is changing at the rate of 4 Tesla/ s, then induced emf in the coil will be:

The capacitor of capacitance 4μF and 6 μF are connected in series. A potential difference of 500 volts applied to the outer plates of the two capacitor system. Then the charge on each capacitor is numerically

(a) 6000 C

(b) 1200 C

(c) 1200 μC

(d) 6000 μC

In a PN-junction diode not connected to any circuit

(a) The potential is the same everywhere

(b) The P-type is a higher potential than the N-type side

(c) There is an electric field at the junction directed from the N- type side to the P- type side

(d) There is an electric field at the junction directed from the P-type side to the N-type side

The maximum efficiency of full wave rectifier is

(a) 100%

(b) 25.20%

(c) 40.2%

(d) 81.2%