D R1907 Pages: 3

13 A magnetic core in the form of a closed ring has a mean length of 20 cm and
cross sectional area of | cm? .The relative permeability of iron is 2400. What
direct current will be needed in a coil of 2000 turns uniformly wound around
the ring to create a flux of 0.2 mWb? If an air gap of Imm is cut through the
core, what current will now be needed to maintain the same flux in the air gap?
What fraction of the ampere turns is required to maintain the flux in the air
gap?

14 Evaluate the power delivered by the 2V source in the circuit below using mesh
current method.

19
‏بت‎ 12
್ಕಗೈಗೆ
2 1A 20
15 Determine rms and average values of the given waveform:

16 Find the total current taken by a parallel circuit connected across a 200 V 50 Hz
supply. The parallel circuit is made up of three branches having impedances
of(6 + j8).2, (4 - j3).2 and (20 - j10).2. Also find the power factor of the
whole circuit. Use admittance method.

PART ^
Answer any one full question from each module, each carries10 marks.
Module V

17 An inductive coil of resistance 10 9, and an inductance of 20 mH are
connected in series with a capacitor of 10 pF. Calculate the frequency at which
the circuit resonate. If a voltage of 50 V at resonant frequency is applied across
the circuit, calculate the voltage across the circuit components and the Q factor.

18 When a 230 V, 50 Hz supply is applied across a resistor of 10 Q in parallel
with a pure inductor, the total current drawn from the supply is 25 A. When the
supply frequency is changed, the total current drawn is 36 A. Calculate the new
frequency.

Module VI
19 a) A 3 phase four wire 400۷, RYB system supplies a star connected load with

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