show that power dissipated by a pure inductor exited by a
sinusoidal voltage source v = vm sin wt is zero
Answer Posted / sarmadahmed
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 View All Answers
How much costly in percentage wise is sandwich busduct costly than air insulated busduct of any rating?
we have earthmat at 110KV substation.we would like to take earth resistance.b some says that by connecting earth megger terminals (C1,P1) at middile point of earthmat (at riser) will cause voltage gradient at other earthmat nods and dont get exat earth resistance.when connecting at end nods will get exat value . is it correct .please explain
Differentiate between kirchhoff’s first law and kirchhoff’s second law?
how does the terminal voltage of transmission lines increase when a capacitor is connected???? This happens not only in transmission lines but also in all circuits. How??? When a capacitor is connected in a transmission line, capacitor also takes energy from the same supply. But how is it able to increase the terminal voltage??? Practically What sequence of events happen during increase in voltage???
Why field rheostat is kept in minimum position?
How to calculate the electrical load for a standard telecom BTS shelter and choose the DG set capacity for the same load?
What is the classification of hydro projects based on installed capacity?
What is the working principle of MIG welding? and its out put Voltage?
what is data block in plc ? How the values of data block are written and read by hmi ? what is the difference between function and function block ?
what curve and rateing would you use for a three phase 0.75kw motor?
Phase control and integral control are used for?
Whether 3 phase induction motorwith 100 hp capacity , Amp 160 for which sensitive earth fault relay , type CTUM 15 can be used?
What type interview questions ask in Electrical technicians
What is d main advantage of using double circuit 3 phase transmission ?
Please define ampere?