Homework Help: Magnetic Flux of Earth onto myself

1. Mar 1, 2009

carrotcake10

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

Estimate the magnetic flux (due to the Earth's field) through your body (back to front) if you stand facing North. What will be the net change in flux if you turn and face South?

2. Relevant equations

Gauss's Law and variants
$$\oint E\bullet dA$$

3. The attempt at a solution
In the past, for simple problems we would always just basically do Qenclosed/Epsilon0.
But to be honest, I don't know where to head in this case.
This problem is suppose to be more conceptual than an actual answer, but I'm missing something apparently.

If someone could point me in the right direction it would be greatly appreciated.

2. Mar 1, 2009

Vuldoraq

I think it is pretty musc the same as your electirc flux questions.

$$\int B\bullet dA =\phi_{m}$$

Since you will be orthogonal to the B field, and the B field is constant the integral becomes trivial, and is just your bodies surface area. Provided your at the equator.

3. Mar 1, 2009

carrotcake10

Good point about where I am standing. I guess my prof overlooked that part of the question. But lets assume I am at the equator. Would I be using the equation B * A? B being the force of the Earth's magnetic field, and A being my body's surface area?

4. Mar 1, 2009

Vuldoraq

Yes, I think so. You can probably assume also that your are two-dimaensional (ie no depth) or treat yourself like a uniform cylinder.

5. Mar 1, 2009

carrotcake10

Just a quick clarification, sorry. Would I be using the surface area of my body, or the surface area of the earth? I would almost think the surface area of my body would be negligible.

6. Mar 1, 2009

Vuldoraq

The question asks for the flux through your body, so it would be silly not to use that. Your right, compared to the size of the Earth you are tiny, but that is irrelevant here. Flux is relative to the area and the field strength, nothing else matters. Hope this helps (Sorry, I'm in the UK and it is getting late here, so I'm a bit tired).

7. Mar 1, 2009

carrotcake10

Sure does, thanks for all your help.