Magnetism And Matter — Physics STD 12 Science — Question

What happens to the wavelength of a photon after it collides with an electron?

The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

(a) 540 nm

(b) 400 nm

(c) 310 nm

(d) 220 nm

An engine uses 30A of current. The resistance offered is 15 ohms. Calculate the power consumed by the engine in horse power.

Two ends of a conductor are at different temperatures the electromotive force generated between two ends is

(a) Seebeck electro motive force (e.m.f.)	(b) Peltier electro motive force (e.m.f.)
(c) Thomson electro motive force (e.m.f.)	(d) None of these

When air in a capacitor is replaced by a medium of dielectric constant K, the capacity:

Assertion  : When PN-junction is forward biased then motion of charge carriers at junction is due to diffusion. In reverse biasing. The cause of motion of charge is drifting.

Reason     : In the following circuit emitter is reverse biased and collector is forward biased.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

When  ampere current is passed in a tangent galvanometer, there is a deflection of 30° in it. The deflection obtained when 3 amperes current is passed, is

(a) 30°

(b) 45°

(c) 60°

(d) 75°

Boolean expression for NAND gate is :

To get an output 1 from the circuit shown in the figure, the input must be

(a) A = 0, B = 1, C = 0

(b) A = 1, B = 0,  C = 0

(c) A = 1, B = 0, C = 1

(d) A = 1, B = 1, C = 0