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Electronics homework help? Please.?
A 500 milliHenry inductor and a 10 kilOhm resistor are connected in series to a 25Volt sourse. What will be the voltage across the inductor 100 microSeconds after energizing the circuit?
I got 0.05 microHenries... But I definately think it's wrong!! Help me please??
1 Answer
- 1 decade agoFavorite Answer
Ok, the answer can't be microHenries because they are asking for voltage. So the answer has to be in volts.
Voltage across an inductor is V= L*di/dt which is a fancy way of saying voltage equals the Inductance times the change in current in a certain amount of time.
Here's the hard part. For now just accept it, but it is derived from the fact that current through an inductor changes exponentially over time due to the magnetic field created in the inductor. Anyway, it's:
di/dt = (V/L)e^-(R/L)t where V is the voltage, L is the inductance, R is the resistance, and t is the time. Plugging in all those values:
di/dt = (25/.5)e^-(10k/.5)(.0001) = (50)(.135) = 6.77
So, Voltage across the inductor is (.5)(6.77) = 3.38V
