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Derived the expression for voltage

by lostinhere
Tags: derived, expression, inductors, voltage
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Mar3-06, 02:18 AM
P: 12
The current in a 15 millihenry inductor is known to be:
i = 4 amperes, for t < 0 and
i = A1 * e -2000*t + A2 * e -8000*t amperes, for t > 0

The voltage across the inductor (assuming the passive sign convention) is 58 volts at t = 0(+) seconds.

I need to find the constants a1 and a2. I have already derived the expression for voltage @ t=0: 58=-30(a1+4*a2).

Unfortunately, I am now lost. I cannot figure out an equation with 2 unknowns. Any help would be greatly appreciated.

I don't believe the fact that i = 4 amperes, for t < 0 is significant for this part of the problem.
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Mar3-06, 02:50 AM
P: 12
never mind, I was overthinking the problem.
Mar3-06, 07:41 AM
Astronuc's Avatar
P: 21,887
Quote Quote by lostinhere
never mind, I was overthinking the problem.
Occupational hazard of smart people.

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