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Electronics/Self inductance


Hi, I have a question about self induction in pure inductors.
If a voltage V is applied across a pure inductor, I understand that the current rises steadily while the magnetic flux stored by the coil increases at the same rate. The voltage across the inductor is equal to the applied voltage. But is this the induced emf as per Lenz's law? If so, shouldn't this voltage oppose the applied voltage and cancel it out? If it cancels it out, then there cannot be any current through the inductor right? I have been breaking my head over this for a long time and would like your help in understanding them clearly.


You are correct.  At the first application of the voltage across the coil there is no  current flowing but with time it increases exponentially until the power supply is overloaded!

And, yes, Lenz law is a good explanation.

But the rate of current increase is a function of the inductance of the coil and the resistance in the circuit  (the ideal inductor of zero resistance is impossible because the coil wire wrapped around the coil form has some resistance, even though quite small).

It is important to understand this phenomenon as well as the similar but opposite effect when voltage is applied to a capacitor.  Then when these are used in combination for tuned circuits you will be more able to understand how they function in filters and bandpass combinations with high frequency alternating currents and voltages.

Let me know if there is more you need to know.  


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Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

BSEE University of North Dakota

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