Peoples Physics Concepts

http://www.ck12.org Chapter 14. Magnetism

Sometimes, it is necessary to represent such three dimensional fields on a two dimensional sheet of paper. The

following example illustrates how this is done.

In the example above, a current is running along a wire towards the top of your page. The magnetic field is circling

the current carrying wire in loops which are perpendicular to the page. Where these loops intersect this piece of

paper,we use the symbol

⊙

to represent where the magnetic field is comingout of the pageand the symbol

⊗

to

represent where the magnetic field is goinginto the page.This convention can be used for all vector quantities:

fields, forces, velocities, etc.

Example 1

You are standing right next to a current carrying wire and decide to throw your magnetic field sensor some distance

perpendicular to the wire. When you go to retrieve your sensor, it shows the magnetic field where it landed to be

4 ∗ 10 −^5 T. If you know the wire was carrying 300A, how far did you throw the sensor?

Solution

To solve this problem, we will just use the equation given above and solve for the radius.