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A192008 Pages: 3
142

Derive an expression for dynamically induced emf in a moving conductor, placed
in a uniform magnetic field of flux density B Tesla.

Tabulate the similarities and dissimilarities of electrical circuits and magnetic
circuits.

Define permeability and relative permeability.

A steel ring has a circular cross-section of area 20 mm? and an average flux path
length of 4 m. An air gap of length 10 cm is cut across the ring. Obtain the mmf
required to establish a flux of 3 mWb in the air gap. Assume the relative
permeability of steel as 1000.

A current of 5A flows through a non inductive resistance in series with a choke coil
when supplied at 250V, 50Hz. If the voltage across the resistance is 125V and that
across the coil is 200V, calculate (i) Impedance, reactance and resistance of the coil (ii)
Power absorbed by the coil and (iii) Total power absorbed by the circuit.

Two impedances 21 and 22 when connected separately across a 200 ۷ 50 Hz supply
consume powers of 100 W and 60 W at power factors of 0.5 lagging and 0.6 leading
respectively. If the impedances are now connected together in series across the same
supply, determine the power absorbed and resulting power factor.

A resistance R, an inductance L = 0.01H and a capacitance C are connected in series.
When a voltage v = 400 cos(3000t — 10) V is applied to the series combination, the
current flowing 103/2 cos(3000t — 55) A. Find R andC.

PART C
Answer any one full question from each module, each carries10 marks.
Module V
Calculate the value of 8) in the circuit given such that circuit will resonate.

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