1. Oscilloscope measurements indicate that the
voltage across a load and the current
through it are, respectively, 210∠60° V and
8∠25° A . Determine:
(a) the real power
(b) the apparent power
(c) the reactive power
(d) the power factor
2. A 120-V rms, 60-Hz electric hair dryer
consumes 600 W at a lagging pf of 0.92.
Calculate the rms-valued current drawn by the
dryer.
3. A 240-V rms 60-Hz supply serves a load that
is 10 kW (resistive), 15 kVAR (capacitive),
and 22 kVAR (inductive). Find:
(a) the apparent power
(b) the current drawn from the supply
(c) the kVAR rating and capacitance required to
improve the power factor to 0.96 lagging
(d) the current drawn from the supply under the
new power-factor conditions
4. Two loads connected in parallel draw a total
of 2.4 kW at 0.8 pf lagging from a 120-V
rms, 60-Hz line. One load absorbs 1.5 kW at a
0.707 pf lagging. Determine: (a) the pf of
the second load, (b) the parallel element
required to correct the pf to 0.9 lagging for the
two loads.
5. Three loads are connected in parallel to a
120∠0° V rms source. Load 1 absorbs 60
kVAR at pf = 0.85 lagging, load 2 absorbs 90 kW
and 50 kVAR leading, and load 3
absorbs 100 kW at pf = 1. (a) Find the equivalent
impedance. (b) Calculate the power
factor of the parallel combination. (c) Determine
the current supplied by the source.
1. Oscilloscope measurements indicate that the
voltage across a load and the current
through it are, respectively, 210∠60° V and
8∠25° A . Determine:
(a) the real power
(b) the apparent power
(c) the reactive power
(d) the power factor
2. A 120-V rms, 60-Hz electric hair dryer
consumes 600 W at a lagging pf of 0.92.
Calculate the rms-valued current drawn by the
dryer.
3. A 240-V rms 60-Hz supply serves a load that
is 10 kW (resistive), 15 kVAR (capacitive),
and 22 kVAR (inductive). Find:
(a) the apparent power
(b) the current drawn from the supply
(c) the kVAR rating and capacitance required to
improve the power factor to 0.96 lagging
(d) the current drawn from the supply under the
new power-factor conditions
4. Two loads connected in parallel draw a total
of 2.4 kW at 0.8 pf lagging from a 120-V
rms, 60-Hz line. One load absorbs 1.5 kW at a
0.707 pf lagging. Determine: (a) the pf of
the second load, (b) the parallel element
required to correct the pf to 0.9 lagging for the
two loads.
5. Three loads are connected in parallel to a
120∠0° V rms source. Load 1 absorbs 60
kVAR at pf = 0.85 lagging, load 2 absorbs 90 kW
and 50 kVAR leading, and load 3
absorbs 100 kW at pf = 1. (a) Find the equivalent
impedance. (b) Calculate the power
factor of the parallel combination. (c) Determine
the current supplied by the source.
