# Homework Help: Inductance of inductor

1. May 2, 2007

### johnboy14

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

a non inductive resistor passes a current of 20A rms, when connected to a 100v rms supply (50HZ). When connect in series with a pure inductor across a 230v supply the combination draws a current of 15A calculate impedance of the circuit, inductance of the inductor

3. The attempt at a solution

R = 100v/20A = 5 ohms

Z = V/I

Z = 230/15 = 15.3

z = square root R^2 + X^2 Find X^2

Z^2 - R^2 = X^2

SRoot 15.3^2 - 5^2 = 14.45 ohms

From what I found how do I find the inductance of the inductor. I only know one way using flux density but there is no data given on this in the question.

2. May 2, 2007

### johnboy14

I know that the formula for reactance is Xl = 2(pi) f L
How do I find L thats the just of what I want.

3. May 2, 2007

### SGT

You know that $$X_L = 14.45\Omega$$ anf f = 50Hz.

4. May 3, 2007

### johnboy14

Do yous get 21.7 for L

5. May 3, 2007

### SGT

I found 0.0458H

6. May 4, 2007

### johnboy14

How did you get that

7. May 4, 2007

### SGT

$$L=\frac{X_L}{2\pi\,50}=\frac{14.45}{314.16}=0.0458H$$

8. May 4, 2007

### johnboy14

I see I made a substitution mistake in my forumla I devided by XL thanks for the help