Electromagnetic Waves — Physics STD 12 Science — Question

The maximum efficiency of full wave rectifier is

(a) 100%

(b) 25.20%

(c) 40.2%

(d) 81.2%

The AC voltage across a resistance can be measured using:

Solar spectrum is an example of:

In the hysteresis cycle, the value of H needed to make the intensity of magnetism zero is called:

The concept of stationary orbits was proposed by

(a) Neil Bohr

(b) J.J. Thomson

(c) Ruther ford

(d) I. Newton

The photoelectric effect can be understood on the basis of

(a) The principle of superposition	(b) The electromagnetic theory of light
(c) The special theory of relativity	(d) Line spectrum of the atom

Faraday's laws are consequence of conservation of

(a) Energy	(b) Energy and magnetic field
(c) Charge	(d) Magnetic field

Among the following _____ has the highest retentivity.

A conducting ring is placed around the core of an electromagnet as shown in fig. When key K is pressed, the ring

(a) Remain stationary

(b) Is attracted towards the electromagnet

(c) Jumps out of the core

(d) None of the above

An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used, same water boils in 10 minutes. If the two coils, connected in parallel are used simultaneously, the same water will boil in time

(a) 3 min 20 sec

(b) 5 min

(c) 7 min 30 sec

(d) 2 min 30 sec