Current and Time in RL Circuit

[musiliu]

Homework Statement

An emf of 10V is connected to the RL circuit (R = 10 Ohms, L = 1.0 H)
shown below for long, long time (the switch is in position 1). Then, at t = 0
the switch is thrown into position 2. Find the current in the circuit at t = 0.2
s. When will the current drop to 0.001 A?
[PLAIN]http://img132.imageshack.us/img132/5139/physicsproblem.jpg

Homework Equations

"Discharge" of RL circuit: I(t) = I₀e^-Rt/L

The Attempt at a Solution

Part 1:
This looks like simple plug-in problem:
I₀ = E / R after "long, long time"
E = 10 V, R = 10 Ohms, L = 1 Henry
I(0.2) = 0.135 A

Part 2:
I set I = .001 A and solved for t:
t = 0.691 s

Are my answers correct and did i do this problem correctly?

 

[Mindscrape]

What did you use as Io, how did you do part 2?

 

[musiliu]

I used Io equal to E / R, voltage over resistance from Ohm's Law, because for "long, long time", the initial current is equal to that...

so is my answer correct?

 

[ehild]

Your answers are correct. ehild

 

[rwisz]

I cannot confirm the accuracy of your answers without reviewing your calculations and methodology. However, your approach seems reasonable and the equations you used are appropriate for solving this problem. I would suggest double checking your calculations and units to ensure accuracy. Additionally, it may be helpful to plot the current vs. time graph to visualize the behavior of the circuit and confirm your answers.