Describe 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) 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.
State the two Kirchhoff's laws. Explain briefly how these rules are justified.
Kirchhoff’s First Law or Junction Rule states that “The sum of the currents flowing towards a junction is equal to the sum of currents leaving the junction.”
This is in accordance with the conservation of charge which is the basis of Kirchhoff’s current rule.
Here, I1, I2 I3, and I4 are the currents flowing through the respective wires.
Convention: The current flowing towards the junction is taken as positive and the current flowing away from the junction is taken as negative.
I3 + (− I1) + (− I2) + (− I4) = 0
Kirchhoff’s Second Law or Loop Rule states that In a closed loop, the algebraic sum of the emf is equal to the algebraic sum of the products of the resistances and the currents flowing through them.
OR
“The algebraic sum of all the potential drops and EMFs along any closed path in a network is zero.”
For the closed loop BACB:
E1 − E2 = I1R1 + I2R2 − I3R3
For the closed loop CADC:
E2 = I3R3 + I4R4 + I5R5
This law is based on the law of conservation of energy.
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.