Science (English Medium) Class 12 - CBSE Question Bank Solutions

The permanent magnetic moment of the atoms of a material is not zero. The material ________________ .

The permanent magnetic moment of the atoms of a material is zero. The material _________________ .

When a ferromagnetic material goes through a hysteresis loop, the magnetic susceptibility
(a) has a fixed value
(b) may be zero
(c) may be infinity
(d) may be negative

A rod is inserted as the core in the current-carrying solenoid of the previous problem. (a) What is the magnetic intensity H at the centre? (b) If the magnetization I of the core is found to be 0.12 A m⁻¹, find the susceptibility of the material of the rod. (c) Is the material paramagnetic, diamagnetic or ferromagnetic?

An ac circuit consists of a series combination of circuit elements X and Y. The current is ahead of the voltage  in phase by `pi /4` . If element X is a pure resistor of 100Ω ,

(a)  name the circuit element Y.
(b)  calculate the rms value of current, if rms value of voltage is  141V.
(c)  what will happen if the ac source is replaced by a dc source ?

Explain how an unpolarised light gets polarised when incident on the interface separating the two  transparent media.

Distinguish between unpolarized and linearly polarized light.

The figure shows a network of five capacitors connected to a 100 V supply. Calculate the total energy stored in the network.

An ac circuit consists of a series combination of circuit elements X and Y. The current is ahead of the voltage in phase by `pi/4`. If element X is a pure resistor of 100 Ω,

(a) name the circuit element Y.

(b) calculate the rms value of current, if rms of voltage is 141 V.

(c) what will happen if the ac source is replaced by a dc source

When light travels from an optically denser medium to a rarer medium, why does the critical angle of incidence depend on the colour of light?

When a wave is propagating from a rarer to a denser medium, which characteristic of the wave does not change and why?

A point-object is placed on the principal axis of convex spherical surface of radius of curvature R, which separates the two media of refractive indices n1 and n2 (n2>n1). Draw the ray diagram and deduce the relation between the distance of the object (u), distance of the image (v) and the radius of curvature (R for refraction to take place at the convex spherical surface from rarer to denser medium.

A potential difference of 220 V is maintained across 12000 Ω rheostat. Then voltmeter V has a resistance of 6000 Ω and point C is at one fourth the distance from a to b. Then the reading of voltmeter is ______.