Homework Help: Current across resistor and inductor

1. May 2, 2007

verbose

1. The problem statement, all variables and given/known data
I have a resistor and an inductor in series. The current across each is the same, correct? I want to know if I can use Ohm's Law to solve for current across the inductor if I know the Voltage and inductive reactance. Basically, does I = V/X_{L} ?

2. Relevant equations

V = IR
I = V/R

does I = V/ X_{L} ?

3. The attempt at a solution

2. May 2, 2007

HallsofIvy

??What do you mean by X_{L}? I can guess that V is the voltage drop, I the current and R the resistance. Is X_{L} the inductance? If so then, no, the voltage drop over an inductance is NOT given by the same equation as for a resistance. Surely you have that formula in your text?

3. May 2, 2007

verbose

X_{l}

by this i mean inductive reactance...sorry, it's tex syntax for X with L as a subscript. i have the habit of writing all my mathy stuff in latex syntax

4. May 2, 2007

SGT

Yes, $$I = \frac{V_L}{X_L}$$
Notice that $$X_L$$ is dependent of the frequency of $$V_L$$

5. Feb 21, 2009

Foxdove

Forget the problem for a minute, first lets clear up that current isn't across anything. Current flows through and voltage is established across. Like fingers on a chalk board.

6. Feb 21, 2009

mplayer

If those 2 elements are in series (the resistor and inductor) and connected to a voltage source, the current through all elements will be given by:

I = VS / (R + XL)

If the voltage you are talking about is the voltage across the inductor, then yes, the current through all elements will given by:

I = VL / XL