Electromagnetic Waves — Physics STD 12 Science — Question

In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is

(a) 4 : 5

(b) 5 : 4

(c) 5 : 9

(d) 9 : 5

The intensity of the electric field required to keep a water drop of radius  just suspended in air when charged with one electron is approximately (g = 10 newton/kg e =  1.6

(a) 260 volt/cm	(b) 260 newton/coulomb
(c) 130 volt/cm	(d) 130 newton/coulomb

Which of the following is conserved when light waves interfere

(a) Intensity

(b) Energy

(c) Amplitude

(d) Momentum

A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is

(a) 0.2 A

(b) 0.4 A

(c) Zero

(d) 0.1 A

A person uses spectacles of power +2D. He is suffering from

(a) Short sightedness or myopia	(b) Long sightedness or hypermetropia
(c) Presbyopia	(d) Astigmatism

The half life (T) and the disintegration constant (λ) of a radioactive substance are related as

(a) λT  = 1

(b) λT = 0.693

(c)

(d)

A body at rest breaks into two pieces of equal masses. The parts will move

1. In same direction.
2. Along different lines.
3. In opposite directions with equal speeds.
4. In opposite directions with unequal speeds.

An electric dipole consisting of two opposite charges of 2   each separated by a distance of 3 cm is placed in an electric field of 2  N/C. The maximum torque on the dipole will be

(a) 12

(b) 12

(c) 24

(d) 24

Four metallic plates each with a surface area of one side A are placed at a distance d from each other. The plates are connected as shown in the circuit diagram. Then the capacitance of the system between a  and b  is

(a)

(b)

(c)

(d)