Derived the expression for voltage

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SUMMARY

The discussion focuses on deriving the constants A1 and A2 for the current expression in a 15 millihenry inductor, given the voltage across it at t = 0 is 58 volts. The current is defined as i = 4 amperes for t < 0 and i = A1 * e^(-2000*t) + A2 * e^(-8000*t) for t > 0. The equation derived for voltage at t = 0 is 58 = -30(A1 + 4*A2). The user expresses difficulty in solving for the two unknowns A1 and A2, indicating a need for further assistance in this calculation.

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lostinhere
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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.
 
Last edited:
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never mind, I was overthinking the problem.
 
lostinhere said:
never mind, I was overthinking the problem.
Occupational hazard of smart people. :biggrin:
 

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