Activities

1. Start by leaving the magnetic field off, and investigate how the charged particle behaves with just the electric field on. Note that every time you adjust a slider, the simulation re-starts. See what happens as you adjust the mass, charge, initial velocity, and magnitude and direction of the electric field (positive is up, negative is down). In particular, see what happens to the force exerted by the field on the particle as you adjust the sliders.
2. Now, explore what happens with the electric field off and the magnetic field on. Note that positive magnetic field is directed out of the screen, while negative field is directed into the screen. Once again, see how the force exerted on the particle changes as you adjust the values of the various sliders.
3. Now, you should be ready to explore what happens with both fields turned on. See if you can find a situation where, with both fields turned on and exerting forces on the charge in the region of field, the charge passes through the region without being deflected. Do this for a few different speeds. You should find a relationship between the speed of the particle and the ratio of the magnitudes of the two fields when the charge experiences no net force. What is the relationship between the fields?
4. Starting with a situation in which the charged particle passes undeflected through the region of field. Describe what happens when the speed of the particle is then changed so that it is either moving faster or slower when it enters the field (describe what happens in both cases).
5. Let's say that you find a combination of electric and magnetic fields that allows a positively charged particle to pass undeflected through the region of field. Make a prediction: if all you change is the sign of the charge, will the charge still pass undeflected through the field? Try it out, and either explain why it still works, or why it does not work.