# Homework Help: Magnetic Field question

1. Feb 23, 2010

### creativepinky

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

This is a two part question I just want to check I'm on the right track - it just seems too easy to be worth the marks they're given so apologies now if I'm stating the obvious:

a) Write down an equation for the magnitude B of the magnetic field at a distance D away in a vacuum from an infinitely long wire carrying a current i.

b) Find the magnitude and direction of the magnetic field at the point O located at a distance D=10cm form a wire carrying a current i = 1.0A directed into the page.

3. The attempt at a solution

For a) I've got B(D)= (μ_0 i)/2πD

Where μ_0 is the permeability of free space constant at 4π x 10^-7 T m A-1

for b) I've just put the figures into the above equation, giving:

B(D) = (4 x 3.14 x 10^-7) x 1A / (2 x 3.14) x 0.1m

That just seems far too easy - what am I missing? Many thanks

2. Feb 23, 2010

### kuruman

You are missing that this is indeed an easy problem.

I hope you got the direction right in the second part.