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



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

Answer / 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

More Electrical Engineering Interview Questions

in a distribution board,if we have a load and we have selected a cable after making all calcs (Deratings and V.D , ect...) the cable we have selected was 10mm.sq. now, shall the internal cable inside the switchboard should be 10 mm.sq Like the external or it can be Less???? if somebody have an specs or information he can help D:

1 Answers  


What are the two basic types of transformers?

0 Answers  


How to know vacuum in vacuum cylinder of breaker in working condition

0 Answers  


To attain a powerfactor more than .95, how much kvr should we use for 100 HP of current

4 Answers   Bhel, Scooters India,


howmany types of compresor is there? and how to calculate compresor capacity?

3 Answers  






What if high voltage side circuit breaker of a ehv transformer instead of lvcb? Kindly elaborate.

0 Answers   MSETCL Maharashtra State Electricity Transmission Co Ltd,


wht is an AVO metre. and whre it is used?

1 Answers   Mayflower,


What are the limiting factor for controlling maximum hot point temperature within a hydrogen and water cooled generator?

1 Answers  


what is the difference between normal motor and flame proof motor??

1 Answers   PI Industries, SRF,


how to cal calculate capacitance in DC Circuit

1 Answers  


Why more sound is produced in mixer than grinder

2 Answers   Vedant,


pls someone send me sample question papers along with the key.thanks in advance

0 Answers   HPCL,


Categories
  • Civil Engineering Interview Questions Civil Engineering (5084)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4451)
  • Electrical Engineering Interview Questions Electrical Engineering (16631)
  • Electronics Communications Interview Questions Electronics Communications (3918)
  • Chemical Engineering Interview Questions Chemical Engineering (1094)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (239)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3014)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (172)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (25)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)