# H= (NI)/ (2(Pi)r)

1. Nov 14, 2008

### dietwater

1. The problem statement, all variables and given/known data
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2. Relevant equations

H= (NI)/ (2(Pi)r)
V=IR

3. The attempt at a solution

a)

total resitance = 100ohms?
from this would the current be 0.12A

over 1ohm resistor: 0.12V

not sure if this is correct even. Any help would be much appreciated.

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2. Nov 15, 2008

### Defennder

Re: conductance

I think you misread 'H' here. H in the question doesn't refer to the magnetic field strength and the formula you provided here refers to the H-field in a torus.

Also in your answer you disregarded the inductor. Bear in mind that once you open the circuit, you can't treat the inductor as a short-circuited wire. What you should do is to write out the KVL loop equation, bearing in mind the potential drop across the inductor is L(di/dt), where i is the time-varying current through the inductor. Then you'll get a differential equation which you then have to solve for the current. Plugging in a initial value will help you find the unknown constant of integration.