Magnetism Demos 3:  Force on a current carrying wire
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	Equipment:

		Lodestar Power Supply (16V, 10 A)
		ring stand with conductor pendulum
		lead (black and red, banana + alligator)
		small horseshoe magnet
		giant horseshoe magnet

	Connect the lead from the power supply to the base of the ring
stand.  Be careful:  the wire suspending the pendulum is quite fine and
it can melt if you put too much current through it.
	Arrange the horizontal bob of the pendulum so that it hangs
between the pole pieces of the small horeshoe magnet.  Now the field
direction is vertical and the current is horizontal (call it East/West)
so the force on the bob will be North/South.  
	Turn down the current limit on the supply, and turn it on.
Increase the current to about 5A.  Now switch if off, let the pendulum
settle down, and switch it back on.  There should be a visible movement
of the pendulum.  Reverse the direction of the current and show that the
force goes the other way.  Reverse the direction of the magnetic field,
and show that the force again reversed direction.

	Repeat with the strong magnet.  The strong magnet, however,
works better with the gap facing up, so the field is then horizonal and
the force is vertical.  When it is upward, it should send the bob flying
upward.  When it is downward, it will pull the pendulum taught.

	Applications:  a basic galvanometer works by the force on the
current carrying coil, as do most electric motors.  A rail gun is
similar to the demo where the bob is launched upwards.