Electricity and Magnetism -- Electromagnetism

Exploring currents and magnetism

Here are some things to do as we begin the section on electromagnetism

Assemble these materials:

6 cm (2.5 inches) of thin copper wire *
a small piece of sandpaper (to take the insulation off of the ends of the wire) *
two battery holders and batteries *
a compass *
a wire with alligator clip ends *
tape

1. Determine which way is north, using a compass, and tape a wire with alligator clip-ends so that a few centimeters in the middle are pointing nearly in the direction of the earth's magnetic field (i.e. whatever direction the compass is pointing). Place the compass on top of the wire.

Now connect one clip to one end of a battery (using a battery holder), and then touch (why?) the other end of the wire to the other end of the battery. Notice what happens to the compass as you connect and disconnect the circuit.
Reverse the battery, so that the current goes the other way. Is the reaction of the compass different?
Reorient the wire, so that now it is running east-west. Now what happens when you start and stop the current?

These experiments were first done by H. C. Oersted in 1819. It was the first time anyone had realized that there is a connection between electricity and magnetism, and led to the invention of the electrical motor.

2. Cut or break a 6 cm piece of the thin wire. Although it looks like copper metal, there actually is a coat of transparent paint on the wire. Scrape off the paint from the last 1/2 cm of each end, using the little piece of sandpaper or a knife (you will see that the bare copper is a brighter, shinier orange). Orient two battery holders (with batteries already in them) plus-to-minus, but then separate them 5 cm apart. making a bridge Put the little wire through the two holes in the ends of the battery holder to make a "swinging bridge" between them. You will have to bend the wire a little bit so that it fits (if it isn't bent already!). The bridge should swing freely, just resting in the little holes of the battery holder.

the magnet has an effect on the wire

Connect a wire to the free end of a battery holder, and again touch the other end of the wire to the remaining free end of the other battery holder, so that we are driving a current through the wire bridge. Nothing interesting will happen (but we have to check!).

Now place a cylindrical magnet under the wire bridge, and start and stop the current.

Turn the magnet over, and see what effect this has.

Hold the magnet at other positions near the wire, and see when the wire responds to the magnet and current.

write in your journal Is there a difference between the first group of experiments (with the compass) and the second set (with the wire), or are they just slightly different ways of showing the same thing? Think about this for a minute, and then see what the professor has to say.

Check the box when you are done:
Next:Making an electromagnet