# Homework Help: Calculate the inductance of a coil of wire

1. Mar 19, 2013

### monnapomona

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

Calculate the inductance (SI units: Henries) of a coil of wire having a loop diameter of 0.5 cm and coil length of 10 cm. The wire has 1000 loops per meter.

2. Relevant equations

I think I can use this equation:
L= μₒAN² / x, x = length of wire, μₒ = 4π*10^-7 Tm/A
A = πr^2

3. The attempt at a solution

L= μₒ(πr^2)N² / x
= μₒ(π(0.0025 m)^2)*(1000^2) / 0.1 m
= 7.85 * 10^-5 H

But apparently on my homework assignment that is wrong. Am I using the wrong formula?

Edit: fixed units

Last edited: Mar 19, 2013
2. Mar 19, 2013

### Staff: Mentor

Take a closer look at your value for N.

3. Mar 19, 2013

### monnapomona

@ gneill: I'm not sure if I'm thinking about this correctly but since I was given 1000 loops per meter, would I have to multiply this by the length (0.1 m) in order to just get the number of loops (N)?

4. Mar 19, 2013

### Staff: Mentor

That would be logical, right?