Physics Test 20...

In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-

Assertion(A): In a meter bridge, if its wire is replaced by another wire having same length, made of same material but having twice the cross-sectional area, the accuracy decreases.

Reason(R): If its wire is replaced by another wire of same material, having same cross-sectional area but of twice the length, accuracy increases.

In a nuclear reactor heavy water is used as a

A disc is placed on a surface of pond which has refractive index 5/3. A source of light is placed 4 m below the surface of liquid. The minimum radius of disc needed so that light is not coming out is

In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-

Assertion(A): Torque is an axial vector and directed along the axis of rotation.

Reason(R): Torque is equal to vector product of force to the position vector.

In order to double the frequency of the fundamental note emitted by a stretched string, the length is reduced to 3/4 th of the original length and the tension is changed. The factor by which the tension is to be changed is

Three sound waves of equal amplitudes have frequencies v − 1 , v , v + 1. They superpose to give beats. The number of beats produced per second will be-

70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from 30^oC to 35^oC. The amount of heat required to raise the temperature of the same sample of the gas through the same range at constant volume is nearly (Gas constant = 1.99 cal/K-mole)

Water is flowing on the blades of a turbine at a rate of 100 kg-s^-1 from a certain spring. If the height of the spring be 100 m, then power transferred to the turbine will be

If the two slits in Young's experiment have width ratio 1:4, the ratio of intensity at maxima and minima in the interference pattern in

Eight negative charges each of value q coulomb are placed at the corners of a cube of side 'a' metre, at the centre of which a positive charge of +2q coulomb is placed.

Q. The central charge 2q makes 8 similar pairs with the charges at corners. Their potential energy is :