Natural Response of an RL circuit

ELECTRONERD

Joined May 26, 2009
1,147
On the first problem in the attached pdf, wouldn't Vo(0-) and Vo(0+) be zero due to the inductor acting as a short?
In terms of resistance, yes, I would say that you're correct. However, inductors do have a negligible amount of resistance that you can ignore, but that certainly doesn't change the inductance. It's still there.
 

Thav

Joined Oct 13, 2009
82
You can only say an inductor acts as a short to DC current. At t=0 there is a transient event in which case the inductor is most decidedly not a short.

The current in an inductor can not change instantaneously. So at t=0+ the current inductor must be the same as it was at t=0-. Where does that current have to flow to complete the circuit? What can you then tell about the voltage across the inductor?
 

ELECTRONERD

Joined May 26, 2009
1,147
You can only say an inductor acts as a short to DC current. At t=0 there is a transient event in which case the inductor is most decidedly not a short.

The current in an inductor can not change instantaneously. So at t=0+ the current inductor must be the same as it was at t=0-. Where does that current have to flow to complete the circuit? What can you then tell about the voltage across the inductor?
That makes perfect sense.
 
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