show that power dissipated by a pure inductor exited by a sinusoidal voltage s

show that power dissipated by a pure inductor exited by a
sinusoidal voltage source v = vm sin wt is zero

Question Posted / mckash

1 Answers
4994 Views
I also Faced
E-Mail Answers

show that power dissipated by a pure inductor exited by a sinusoidal voltage source v = vm sin wt ..

Let Vmcos(wt+X) be the voltage and Imcos(wt+Y) be the current through the inductor.
Now the power is given by
P=V*I=VmImcos(wt+X)cos(wt+Y)
By using a trigonometric identity:
P= 0.5 * VmIm * cos(X-Y) + 0.5 * VmIm * cos(2wt+X+Y)
This expression has 2 terms which both must be zero.
The first term is a constant (independent of time) but notice that in an inductor Voltage leads Current by 90 degrees so X-Y = 90 and cos(90) = 0 so first term is zero.
Now for average power integrate the above expression for a cycle and divide it by time period, since integral of every sinusoid for a complete cycle is zero the next term will essentially be zero too.

So P = 0 for an inductor.

Email me if you still have any doubt or query.
sarmadahmed@live.com

Is This Answer Correct ?

3 Yes

0 No

Post New Answer

More Electrical Engineering Interview Questions

Which motor is 3.3 or 11kV more reliable, in terms of efficeancy,maintenance, reliability.

0 Answers Megatron Solutions, TCL,

Why CT secondary is grounded?

4 Answers

what is different between auto transformer and vriac

4 Answers

Does RCCB do the job of MCB? Lets take 16A RCCB. it trips when residual current exceeds 30mA. does it trip in an over current situation, i.e when current exceeds 16A ??

2 Answers

in three phase with neutral connection, what will happen,if the neutral is in open condition with single phase distribution panel ?

2 Answers

why Current is lead 90 degree and voltage is lag 90 degree in a capacitor.? why Current is lag 90 degree and voltage is lead 90 degree in an inductor.?

0 Answers

WHY SEPARATELY EXCITED MACHINE NEEDS EXCITATION BY DC SUPPLY WHY NOT BY AC

0 Answers

What is pole of the system?

0 Answers

Why we use d.c. meger in a.c. induction motor?

1 Answers

a new 3ph induction motor doesn't rotates their ratted speed, why ?

2 Answers Sail,

what is the difference between MCCB and SFU in terms of their application?

2 Answers Secure Meters, Tata Teleservices,

why do we prefer a 3-phase delta connected load rather than star connected?

4 Answers

For more Electrical Engineering Interview Questions Click Here