13.

14.

15.

16.

17.

18.

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2 C 41238

Section B (Paragraph/Problem Type)

Answer all questions in a paragraph of about half a page to one page, each correct answer

carries a maximum of 5 marks

A long solenoid of radius a is driven by an alternating current so that the field inside is sinusoidal,
given by B (¢) = By cos (at) 2. A circular loop of wire, of radius a/2 and resistance R, is placed
inside the solenoid and co-axial with it. Determine the current induced in the loop as a function of

time.

Show that the radiation pressure caused by an electromagnetic wave is equal to the ratio of the

intensity of the electromagnetic wave and the velocity of light.

A coil of 10 H inductance and 5 Q resistance is connected in parallel with a 20 © resistor across a
100 V d.c. supply, which is suddenly disconnected. Determine the voltage across the 20 Q resistor
initially and after 0.3 s.

A large coil of inductance 1.405 H and resistance 40 Q is connected in series with a capacitor of

20 uF. Determine the frequency at which the circuit resonates.

Give an expression for the power consumed in a series LCR circuit. Show that in a purely inductive

or a purely capacitive circuit, the power consumed is zero.

Use Thevenin’s theorem to determine the current through the 10 Q resistance of the following

circuit :

8Q
pid A
GANA
5Q

20 10೧
201%

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