Capacitors and inductors

  • Thread starter Sastronaut
  • Start date
  • #1
Sastronaut
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Homework Statement


an electromagnet is operated at 50A. assuming an inductance of 100H for the magnet's coil, what voltage will be developed when the switch is opened? when it is closed? assume that the switch requires 1 millisecond to operate.


Homework Equations


I(t) = Vb/(R(1-e^(-tR/L)))


The Attempt at a Solution


with the given formula above I am not quit sure how to proceed if I am not given resistance. any insight on how I should proceed with this problem would be great!
 

Answers and Replies

  • #2
nasu
3,957
582
You could use Faraday's law of induction. It gives you the emf developed by a change in the magnetic flux.
 
  • #3
gneill
Mentor
20,945
2,886
Is there a circuit diagram to accompany this problem? Maybe that would give us a hint as to the where the resistance is supposed to be, or what might be in place to limit voltages, or what the implications are for a switch that "requires 1 millisecond to operate".
 
  • #4
Sastronaut
68
0
no diagram but I figured it out.

di/dt = 50A/10^-7
V = L(di/dt)
V= 5MV
 
  • #5
Sastronaut
68
0
thank you everyone!
 

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