An electrical element draws a current of i(t) –√2 cos100πtA from a sinusoidal voltage
source of v(t) 10√2 sin100πtV. Find and plot instantaneous power delivered to the
load and energy delivered to it as functions of time.
SOLUTION
p(t) –20 sin100
π
t cos100
π
t –10 sin200
π
t W and E(t) –0.05(1 – cos200
π
t) J.
Power waveform has 100 Hz frequency whereas the voltage and current wave-
forms have 50 Hz frequency. The period of the power waveform is 10 ms.
Average value of power over a cycle. Therefore, the
energy function cannot be a growing function. The net change in E(t) over a cycle of
power waveform will be zero. It has to be an alternating ...
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