Long Answer TypeDescribe the working principle of a moving coil galvanometer.
Why is it necessary to use
(i) a radial magnetic field and
(ii) a cylindrical soft iron core in a galvanometer?
Write the expression for the current sensitivity of the galvanometer.
Can a galvanometer as such be used for measuring the current? Explain.
(a) Define the term 'self-inductance' and write its S.I. unit.
(b) Obtain the expression for the mutual inductance of two long co-axial solenoids S1 and S2 wound one over the other, each of length L and radii r1 and r2 and n1 and n2 number of turns per unit length when a current I is set up in the outer solenoid S2.
a) Mutual inductance of two coils is equal to the e.m.f induced in one coil when the rate of change of current through the other coil is unity.
SI unit of mutual inductance is Henry.
b) Consider two long solenoids S1 and S2 of same length ‘l’ such that S2 surrounds S1 completely.
Let,
n1 = Number of turns per unit length of S1
n2 = Number of turns per unit length of S2
I1 = Current passing through solenoid S1
= Flux linked with S2 due to current flowing in S1
is the coefficient of the mutual inductance of two solenoids.
When current is passed through S1, emf is induced in S2 .
Magnetic field inside solenoid S1 is given by, 
Magnetic flux linked with each turn of the solenoid = 
Total magnetic flux linked with S2 is given by,
Similarly, mutual inductance between two solenoids, when current is passed through S2 and emf induced in solenoid S1 is given by, 
Hence, coefficient of mutual induction between the two long solenoids is given by, 
(a) Draw a labelled diagram of a step-up transformer. Obtain the ratio of secondary to primary voltage in terms of number of turn and currents in the two coils.
(b) A power transmission line feeds input power at 2200 V to a step-down transformer with its primary windings having 300 turns. Find the number of turns in the secondary to get the power output at 220 V.
Derive an expression for drift velocity of electrons in a conductor. Hence deduce Ohm's law.
The current is drawn from a cell of emf E and internal resistance r connected to the network of resistors each of resistance r as shown in the figure. Obtain the expression for (i) the current draw from the cell and (ii) the power consumed in the network.
(i) A ray of light incident on face AB of an equilateral glass prism shows the minimum deviation of 30°. Calculate the speed of light through the prism.
(ii) Find the angle of incidence at face AB so that the emergent ray grazes along the face AC.
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