1
$\begingroup$

When an ac source is connected with an inductor we have a continuous change in voltage and current across the inductor.

According to farady and lenz law we will get an equal and opposite voltage against the source voltage for each change of voltage or current across the inductor.

Now since we always get an equal and opposite voltage across the inductor for each change in source voltage so it means that the current will never be able to flow in the inductor but yet current is always flowing in each text book. I am confused about it. Please guide me. I shall be grateful to you. Note that it is an ideal case and we have no resistance in the circuit.

e

$\endgroup$

2 Answers 2

1
$\begingroup$

Now since we always get an equal and opposite voltage across the inductor for each change in source voltage so it means that the current will never be able to flow in the inductor . . . .

This is a common misconception.

For the inductor to generate a voltage $L\frac {dI}{dt}$ the current must be changing ie $\frac{dI}{dt}\ne 0$.

So if the currents starts off as being zero it must change from being zero.

If you think of the process in terms of energy transfer $\rm J$ rather than in terms of voltages $(\rm J/C)$ then what is happening is the voltage source is supplying electrical energy to the inductor which in turn is storing that energy in its magnetic field.
The the reverse process occurs when the magnetic field is decreasing and energy is being returned to the voltage supply.

$\endgroup$
5
  • $\begingroup$ Isnt it true that when we apply a voltage source accros the inductor then initially we get equal and opposite voltage across the inductor against the source voltage. So why is it not true for each change across the inductor? $\endgroup$
    – Alex
    Mar 23, 2020 at 11:19
  • $\begingroup$ I never said it was not so. What I did say is that irrespective of what is happening to the voltages for there to be a voltage across an inductor the current through the inductor must be changing. $\endgroup$
    – Farcher
    Mar 23, 2020 at 11:53
  • $\begingroup$ You said "what is happening is the voltage source is supplying electrical energy to the inductor which in turn is storing that energy in its magnetic field. The the reverse process occurs when the magnetic field is decreasing and energy is being returned to the voltage supply." $\endgroup$
    – Alex
    Mar 24, 2020 at 4:15
  • $\begingroup$ Yes voltage source is supplying energy to the inductor but in this case the energy of the inductor that is spplied by the source comes face to face against the source and stops any change in current in the inductor. $\endgroup$
    – Alex
    Mar 24, 2020 at 4:19
  • $\begingroup$ Your answer on another post made me accept this answer aswell. $\endgroup$
    – Alex
    Mar 27, 2020 at 11:19
1
$\begingroup$

The varying magnetic field around the coil partially resists drift current and every 2/f sc (starting from 4/f sc ) it actually helps it.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.