One application of an RL circuit is the generation of time varying high-voltage from a low-voltage source as shown in the figure.(adsbygoogle = window.adsbygoogle || []).push({});

1257 ohms

14 ohms 2 H (switch) b

a

12.6 V.

Sorry, I couldn't get the picture, but heres a rough idea.. it's in a circuit.

What is the current in the circuit a long time after the switch has been in position "a"?

I got this part... it was0.9 A

Part 2 says: Now the switch is thrown quickly from "a" to "b". Compute the initial voltage across the inductor.

I got this too.. it was1143.9 V

Part 3 says: How much time elapses before the voltage across the inductor drops to 13 V? Answer in units of ms.

I used the equation [tex] I= I_0 e^ (-R/L)t [/tex]

and then figured out that [tex] V= I_0 Re^(-R/L)t [/tex]

so 13.0 V=(0.9)(1143.9)e^(1143.9t/2)

solving for t gave me 7.64 ms which isnt' right.. can someone please help me?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: RL circuit Voltage problem

**Physics Forums | Science Articles, Homework Help, Discussion**