# Homework Help: How do electric and magnetic waves affect each other?

1. May 24, 2010

### MCATPhys

I understand that a stationary charge has an electric field by the equation:

E = kq1q2/r^2

When the charge starts to move, it has an electric field and a magnetic field:

B = ui/(2pi)r

where i is the current and u the permeability of free space. What I don't understand is the cause of electromagnetic waves. More specifically, how does a changing magnetic field cause a change in electric field, and a changing electric field cause a change in the magnetic field. I don't understand how. Can someone show it to me using the eqations.

2. May 24, 2010

### ehild

The behaviour of electromagnetic waves is governed By Maxwell's equations. You need to know vector analysis to fully understand this. There are some good video lectures on the topics, for example that of dr Lewin's: http://videolectures.net/mit803f04_lewin_lec13/

If you are not familiar with curl and divergence yet, keep in mind that electric field causes current, current causes magnetic field. In a changing magnetic field, there will be electromotive force in a closed loop. This causes current of some kind. If the current varies with time, it causes varying magnetic field around the loop and so on.

Be patient, you will learn about it soon!

ehild