Time constant for the current through the inductor

AI Thread Summary
The discussion focuses on calculating the time constant for the current through an inductor in a circuit with a voltage of 6 volts, a resistance of 10 ohms, and an inductance of 100 mH. The correct formula for the time constant is established as τ = 2L/R. A participant initially suggests that the equivalent resistance is 2R, leading to a time constant of L/2R, but this is corrected to R/2, confirming the original time constant of 2L/R. The key takeaway is that the time constant for the current through the inductor is indeed 2L/R.
syhpui2
Messages
23
Reaction score
0

Homework Statement



wjD8Y.png


http://i.imgur.com/wjD8Y.png

In the circuit below, V = 6 volts, R = 10 ohms, L = 100 mH. The switch has been open for a long time. Then, at time t = 0, the switch is closed.



What is the time constant for the current through the inductor?

2L / R


Homework Equations



TAU=l/R

The Attempt at a Solution



I am not sure how do I find the equvialent resistance in this case.
 
Last edited:
Physics news on Phys.org
Kill the source (short the voltage supply) and remove the inductor. Find the equivalent resistance at the terminals where the inductor was.

attachment.php?attachmentid=40334&stc=1&d=1319604076.gif
 

Attachments

  • Fig1.gif
    Fig1.gif
    2.2 KB · Views: 637
gneill said:
Kill the source (short the voltage supply) and remove the inductor. Find the equivalent resistance at the terminals where the inductor was.

attachment.php?attachmentid=40334&stc=1&d=1319604076.gif


Equvialent resistance is 2r then time constant should be L/2R?

instead of 2L/R?

Thanks
 
syhpui2 said:
Equvialent resistance is 2r then time constant should be L/2R?

instead of 2L/R?

Thanks

Nope. Those two resistors are not in series with respect to the open terminals. So the resistance is R/2. That makes your time constant 2L/R.
 
Thread 'Struggling to make relation between elastic force and height'

Thread 'Struggling to make relation between elastic force and height'

Hello guys this is what I tried so far. I used the UTS to calculate the force it needs when the rope tears. My idea was to make a relationship/ function that would give me the force depending on height. Yeah i couldnt find a way to solve it. I also thought about how I could use hooks law (how it was given to me in my script) with the thought of instead of having two part of a rope id have one singular rope from the middle to the top where I could find the difference in height. But the...
View full post »
Thread 'Voltmeter readings for this circuit with switches'

Thread 'Voltmeter readings for this circuit with switches'

TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
View full post »

Similar threads

Current through an inductor as a function of time
Replies
10
Views
450
Symmetrical parallel inductors, different currents? State Preparation
Replies
7
Views
1K
Solving Inductor Circuit Homework Problems
2
Replies
52
Views
13K
Current through an inductor after a switch closes
Replies
4
Views
3K
Potential Drop Across 15-mH Inductor at t=0?
Replies
5
Views
2K
Find current through inductor after many time constants.
Replies
2
Views
4K
What is the maximum value of the current through the inductor?
Replies
34
Views
7K
Determining Inductance L in an LC Circuit
Replies
5
Views
2K
What is the maximum current in a RL circuit using V=IR?
Replies
13
Views
2K
Calculation of current in driven series RLC circuit
Replies
8
Views
2K

Hot Threads

Recent Insights

Back
Top