A resistance of 20 W and a coil of
inductance 31.8 mH and negligible resistance
are connected in parallel across 230 V, 50 Hz
supply. Find (i) The line current (ii) power
factor and (iii) The power consumed by the
c
...
A resistance of 20 W and a coil of
inductance 31.8 mH and negligible resistance
are connected in parallel across 230 V, 50 Hz
supply. Find (i) The line current (ii) power
factor and (iii) The power consumed by the
circuit.
2. Two impedances Z1 = (150 + j157) ohm
and Z2 = (100 + j 110) ohm are connected in
parallel across a 220-V, 50-Hz supply. Find
the total current and its power factor.
3. Two impedances (14 + j5) Ω and (18 + j10)
Ω are connected in parallel across a 200-V,
50-Hz supply. Determine (a) the admittance
of each branch and of the entire circuit; (b)
the total current, power, and power factor and
(c) the capacitance which when connected in
parallel with the original circuit will make the
resultant power factor unity.4. A parallel circuit consists of two branches
A and B. Branch A has a resistance of 10 Ω
and an inductance of 0.1 H in series. Branch
B has a resistance of 20 Ω and a capacitance
of 100 μF in series. The circuit is connected
to a single-phase supply of 250 V, 50 Hz.
Calculate the magnitude and the phase angle
of the current taken from the supply. Verify
your answer by measurement from a phasor
diagram drawn to scale.
5. Two circuits, the impedances of which are
given by Z1 = (10 + j15) Ω and Z2 = (6 −j8)
Ω are connected in parallel. If the total
current supplied is 15 A, what is the power
taken by each branch?
6. A voltage of 240 V is applied to a pure
resistor, a pure capacitor, and an inductor in
parallel. The resultant current is 2.3 A, while
the component currents are 1.5, 2.0 and 1.1 A
respectively. Find the resultant power factor
and the power factor of the inductor.
7. Two parallel circuits comprise respectively
(i) a coil of resistance 20 Ω and inductance
0.07 H and (ii) a capacitance of 60 μF in
series with a resistance of 50 Ω. Calculate the
current in the mains and the power factor of
the arrangement when connected across a
200-V, 50-Hz supply.
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