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12801 Pages: 3

Figure 1. Figure 2.

Use star-delta/ delta- star transformation to determine the equivalent resistance
between the points A and B of the circuit shown in Fig. 2. All the values of the
resistances are in (2.

A closed magnetic circuit of cast steel contains a 6cm long path of cross-sectional
area 1 cm’and a 2cm path of cross-sectional ೩1೨೩ 0.5 cm’. A coil of 200 turns 15
wound around the 6 cm length of the circuit and a current of 0.4 A flows through
it. Determine the flux density in the 2 cm path of the magnetic circuit.
Relative permeability of cast steel is 750.

Derive an expression for dynamically induced emfin a moving conductor in terms
of magnetic flux density (B), length of the conductor(/), velocity(v) and the
angle between B and v

Tabulate thesimilarities and dissimilarities of electrical circuits and magnetic
circuits

A hollow air cored inductor coil consists of 500 turns of copper wire which
produces a magnetic flux of 10mWb when passing a DC current of 10 A.

(i) Calculate the self-inductance of the coil in mH.

(ii) calculate the value of the self-induced emf produced in the same coil after a
time of 10ms.

Find the total voltage across the terminals

A and B of the circuit shown in Fig. 3. 3Z0° 42180”

Draw the waveforms of the 4018205320, [< <~]
۱ ۱

42180” and Vag.

Figure 3.

A series circuit consisting of a capacitor of 2 [7 and a resistance of 500 ൮. An AC
source is connected to the circuit which draws a current of 5020 mA. The angular
frequency of AC source is 4002.(1) draw the circuit and find the source voltage
(ii) find the voltage across the capacitor and resistor (iii)draw the voltage phasor
diagram.

A three-phase load consumes 100 kW, and 50 kVAR. Determine the apparent
power and the power factor angle.

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