# Can an Inductor hold a charge?

1. Jul 21, 2010

### physMommy

I understand that in an ideal world, an inductor will not hold a charge (when not connected to a circuit). Ideally, there would need to be a current through the inductor to generate a B-field to store energy.

I once read, that (since this is not an ideal world), an inductor actually CAN and WILL hold a charge, rather than fully discharging when disconnected from a circuit.

I'm looking for a valid argument either way.

Thanks!

2. Jul 21, 2010

### AJ Bentley

It can't hold a charge, but a superconducting inductor can hold a current.

Which means that it retains it's magnetic field in the same way as a magnet holds it's field.

3. Jul 21, 2010

### physMommy

Let me explain where I'm coming from with this.
I was told I needed to discharge an inductor used in a simple LR circuit before completing the circuit.
Theoretically, this makes no sense as the inductor should not be charged/storing energy outside of a circuit.
Is there really a need to discharge an inductor prior to introducing it to a circuit?
I did read that in actuality, an inductor will store energy independently, to some degree.
Is this possible?

4. Jul 21, 2010

### AJ Bentley

No, that makes no sense.

You might need to slowly power down a big inductor before trying to disconnect it because it may arc over if you break the circuit suddenly. (Current continues to flow because of electromagnetic inertia).

In the short term, an inductor stores energy in it's field during operation, but we're talking about fractions of a second. That energy dissipates when the circuit is broken and is gone when the current reaches zero.

Contrast the charge holding properties of a capacitor which may hold a lethal charge for several minutes or even hours if it's big enough.

5. Jul 21, 2010

### physMommy

Thanks, AJ!
This confirms my thoughts.

I did google the topic before and found a source which said an inductor will hold a charge/energy and needs to be discharged, but I am unable to locate that source, now. It was something I came across and wanted to verify the reliability of the source.