# Practical investigation on motors and generators

I'm not sure on what I have to do for this practical. I have to develop a theory and choose certain equipment for me to perform the investigation and obtain results... only i dont know where to start.

the aim is:
Investigate how the amplitude of a pendulum formed by a magnet and thread varies against time with or without a nearby electrical conductor.

Any ideas?!

The changing magnetic field will generate eddy currents in the conductor, so I'm thinking the amplitude of the pendulum would decrease as energy is lost to heat through I^2 R.

A similar effect happens when you drop a strong magnet in a copper tube. It appears to defy gravity as it floats very slowly down the tube before falling out the other end. (Neat to watch...try it if you can find the materials)

Of course, there is probably more going on than that, but it's a start.

thanks PBRMEASAP!! that was a great start :tongue: at least i think im understanding abit more!! thanks!!!!

applepie said:
thanks PBRMEASAP!! that was a great start :tongue: at least i think im understanding abit more!! thanks!!!!

It sounds like a really cool experiment. Let us know what you find out!

does anyone know how to measure the amplitude??
time is with stopwatch right??
hope some one can help!

Make yourself a protractor out of cardboard and attach it to the pivot of the pendulum somehow (but don't let it interfere with the pendulum swing). Make it nice and big so that you can easily "eyeball" the angle the string makes with the vertical at maximum displacement. The pendulum should stay swinging for quite a while, so it should be sufficient to take a measurement every few swings, giving you time to write your measurement down. Yes, use a stopwatch to note the time at each measurement.