# Homework Help: Magnetic Moment

1. Aug 13, 2009

### iontail

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

find the magnetic moment of a hydrogen atom given that the election moves at 0.10c around the nucleus and the radius is 0.5*10^-5 m

2. Relevant equations

n/a

3. The attempt at a solution

this is what i did.

I = nev
=ev (I = current e= charge of electron, v = velocity)

m = IA (A = area)

my result is 12 A m^2.

The result looks too big...am I doing something wrong. can you please verify that my answer is right.

2. Aug 13, 2009

### Staff: Mentor

What's n?

Hint: Find the current by figuring out long it takes for the electron to orbit the nucleus.

3. Aug 13, 2009

### jpreed

e = 1.6*10^-19 coulomb
v = 3*10^7 m/s
r = 0.5*10^-5 m

I = q v
m = I pi r^2

I get:

I = 4.8*10^-12
m = 3.77*10^-22

4. Aug 13, 2009

### Staff: Mentor

You might want to rethink that equation.

5. Aug 13, 2009

### iontail

n=number of free electron

and I = nev/(r*pi*r) (r= radius of atom)

the answer i got before is still correct. I just made a typo while putting the detials in the computer.

I am just suprised that the magnetic moment for an atom is so high. CAn you please verify the answer. or tell me if i have made any other mistake.

6. Aug 13, 2009

### Staff: Mentor

OK, so n = 1.

That doesn't look right. (Check the units.)

7. Aug 14, 2009

### iontail

I = ev/2*pi*r

it should be right now.

8. Aug 14, 2009

### Staff: Mentor

Now you've got it.

9. Aug 14, 2009

### jpreed

Oops, I forgot to normalize by the distance. You are right.

It should be

I = q v / (2 pi r)

10. Aug 14, 2009

### iontail

thabk you all for you help...