Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Write current sensitivity of a galvanomete S.I. unit. 

Figure shows two circuits each having a galvanometer and a battery of 3V.

When the galvanometers in each arrangement do not show any deflection, obtain the ratio R₁/R₂.

Define electric dipole moment. Is it a scalar or a vector? Derive the expression for the electric field of a dipole at a point on the equatorial plane of the dipole.

Distinguish between ‘Analog and Digital signals’.

Write any two factors which justify the need for modulating a signal ?

Draw a diagram showing an amplitude modulated wave by superposing a modulating signal over a sinusoidal carrier wave.

Explain, giving reasons, the basic difference in converting a galvanometer into (i) a voltmeter and (ii) an ammeter?

How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.

Define dipole moment of an electric dipole. Is it a scalar or a vector?

Draw a labelled diagram of a moving coil galvanometer and explain its working. What is the function of radial magnetic field inside the coil?

Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1  +1/f_2`for two thin lenses kept in contact coaxially.

Define electric dipole moment. 

In the meter bridge experiment, balance point was observed at J with AJ = l.

(i) The values of R and X were doubled and then interchanged. What would be the new position of balance point?

(ii) If the galvanometer and battery are interchanged at the balance position, how will the alance point get affected?

Write briefly any two factors which demonstrate the need for modulating a signal. Draw a suitable diagram to show amplitude modulation using a sinusoidal signal as the modulating signal.

State the principle of the working of a moving coil galvanometer, giving its labeled diagram ?

Outline the necessary steps to convert a galvanometer of resistance RG into an ammeter of a given range ?

In which orientation, a dipole placed in a uniform electric field is in (i) stable, (ii) unstable equilibrium?

Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.

State the underlying principle of working of a moving coil galvanometer. Write two reasons why a galvanometer can not be used as such to measure current in a given circuit. Name any two factors on which the current sensitivity of a galvanometer depends.

A normal eye is not able to see objects closer than 25 cm because