# Capacitors in magnetic fields?

1. Oct 1, 2009

### physguy09

I have been trying to do some research, but the more I search, the more confused I get (praise physics for that one). In anycase, I know that a charge moving through a magnetic field creates a current, so lets say we have an initially charged loop moving through a quasi-uniform magnetic field, if we have two plates extending parallel to the power source, that is if we had some sort of battery in this loop, would they charge up as we run them through the magnetic field? And would this charge be a result of the battery, or the fact that they passed through the field?

2. Oct 1, 2009

### Bob S

I am not sure what you mean by charged loop. It is true that currents will be induced in a closed loop of wire, but not in a unifrorm field, unless it is rotated in the field. The Lorentz force can induce voltage in a coil moving in a non-uniform field, but it will not create charge. If you have a shorted loop connected to a battery, it is true that you can induce currents in it, but you will also short out the battery.

If you put a reverse diode in series with the battery, the induced voltage will charge the battery whenever the induced voltage exceeds the battery voltage. This will not discharge the battery. Recently I had to build eight large ferrite magnets oscillating (triangle wave) at about 500 Hz. For a monitor (because the magnets were silent), in the aperture of each magnet I put four turns of wire in series with a 6-volt bulb, which lit up when the magnet was on.
Bob S

Last edited: Oct 1, 2009