# Need help understanding transient inductive networks

When the circuit is in the storage phase is R2 shorted? My professor's PowerPoint shows R2 going away when the switch is connected to the circuit. Why is this? Will this be the same if R1 > R2? Thanks!

When the circuit is in the storage phase is R2 shorted?

No, if R2 was shorted then it will short the supply out when the switch closes.

My professor's PowerPoint shows R2 going away when the switch is connected to the circuit. Why is this?

When the switch connects the power source to the rest of the circuit, R2 plays no significant role in affecting the current into the inductor hence, it can be removed but, has to be reinstated when the switch opens.

Will this be the same if R1 > R2?

It's got nothing to do with values.

• Will this be the same if it was at a steady state? Commented Dec 2, 2023 at 22:10
• I don't understand your comment. Commented Dec 2, 2023 at 22:18

When the circuit is in the storage phase is R2 shorted?

No.
If it was being shorted, then it would cause infinite current to flow from E.

Perhaps the confusion is that the inductor, L, can be considered to be "shorted" after sufficient time has passed after the switch has closed. You can use this to compute the currents flowing in each part of the circuit when the circuit is said to be in the steady-state ie: when the currents and voltages are no longer changing with time. The time needed for steady-state can be taken to be 5 time-constants.

My professor' PowerPoint shows R2 going away when the switch is connected to the circuit. Why is this?

R2 "goes away" because it does not affect the time-varying variables (current, voltage) when the switch is closed. However, in the case where energy has been stored in the inductor, you will find that R2 has a very important role to play after the switch is opened.

Will this be the same if R1 > R2?

Yes. (By "this" I am assuming your are referring to: "professor' PowerPoint shows R2 going away".)

The size of R1 relative to R2 has no bearing on the effect that R2 has on this circuit when the switch is closed. However, in the case where energy has been stored in the inductor, you will find that both R1 and R2 have a very significant impact after the switch is opened.