Introduction to Electric Circuits

106 Single-phase a.c. circuits

a coil of impedance (5 + j7) 1~. Calculate for each case (i) the current

drawn from the supply, (ii) the power supplied, and (iii) the power factor

of the whole circuit.

10 A coil of inductance 15.9 mH and resistance 9 f~ is connected in parallel

with a coil of inductance 38.2 mH and resistance 6 ~ across a 200 V, 50 Hz

supply. Determine (a) the conductance, susceptance and admittance of the

circuit, (b) the current drawn from the supply and (c) the total power

consumed in kW.

11 Three coils are connected in parallel across a 200 V supply. Their

impedances are (10 + j30) ~, (20 + j0) ~ and (1 - j20) II. Determine (a)

the current drawn from the supply and (b) the power factor of the circuit.

12 Determine (a) the current drawn from the supply and (b) the total power

consumed in the circuit of Fig. 4.44.

(4+j6)~

i t

50Hz

(6+j3)~

!!

(5-j8)9.

~1!

Figure 4.44