(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

An RL circuit has a 9.0 V battery and a 5.5 ohm resistor. When the switch is closed, the current in the circuit is observed to increase from 0 to 0.30 A in 0.17 s.

A) What is the inductance?

B) How long after the switch is closed does the current have the value 0.47 A?

2. Relevant equations

τ = L/R

EMF = L*I / t

I = EMF / R *(1-e^-tR/L)

3. The attempt at a solution

I don't know how to find a time constant, my text doesn't explain it, which makes me think that this question may not even use this equation. I can't get to part B without an answer to part A. By using the second equation I got L = 5.1, but that isn't correct.

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# Homework Help: RL circuit inductance problem

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