Solve EMF, Induction Homework Problems

[talaroue]

Homework Statement

1. A 109.3 mH inductor whose windings have a resistance of 3.6 Ω is connected across a 11 V battery having an internal resistance of 1.83 Ω. How much energy is stored in the inductor?

2. The maximum allowable potential difference across a 225.7 mH inductor is 401 V. You need to raise the current through the inductor from 1.28 A to 3.88 A. What is the minimum time you should allow for changing the current?

Homework Equations

EMF(max)=wNBA
w=angular momentum
N=number of loops
B=magnetic field
A=area

The Attempt at a Solution

For both of these what seem to be similar problem I am hitting a dead end!

 

[diazona]

I thought of something entirely different upon seeing wNBA...

Anyway, here's a hint: #1 asks for the energy stored in an inductor. Do you know a formula for that?

For #2, do you know an equation for the voltage (potential difference) across an inductor?

 

[talaroue]

#1 U=.5L*I^2#2
V=-L(dI/dt)

d I= delta flux

 

[diazona]

#1 U=.5L*I^2


#2
V=-L(dI/dt)

Yep, that's right. Note that in both cases, I is electrical current (I hope you knew that).

Now do you have any ideas about how to use those formulas?