# Homework Help: Calculating when voltage across resistor = voltage across inductor in an RL circuit

1. Jan 18, 2013

### JordanU94

1. The problem statement, all variables and given/known data

A step input of 100V is applied to a resistor of 50Ω in series with an inductor of 10H at time t=0. Calculate the time at which the voltage across the resistor equals the voltage across the inductor

2. Relevant equations

Im not sure which equation to use, i know τ=L/R is used, but thats all im certain of

3. The attempt at a solution

I have no valid attempts :grumpy:
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 18, 2013

### Staff: Mentor

Re: Calculating when voltage across resistor = voltage across inductor in an RL circu

Google is your friend. Look up "LR series circuit".

3. Jan 18, 2013

### JordanU94

Re: Calculating when voltage across resistor = voltage across inductor in an RL circu

I have been for the past week, I've found equations to find the current in the circuit, and the time constants of the exponensial curve, but not what I'm looking for

4. Jan 18, 2013

### Staff: Mentor

Re: Calculating when voltage across resistor = voltage across inductor in an RL circu

Well, what equations have you found?