Here are some things to do as we begin the section on electromagnetism
Assemble these materials:
two battery holders and batteries *
a compass *
wires with alligator clip ends *
tape
a piece of aluminum foil 4"x4"
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 the aluminum foil into the shape of an arch.
With the arch lying flat on the table, tape the feet to the table, and then
bend the foil so that the arch stands up.
Attach wires the the feet, so that we can cause
a current to go over the arch.
Briefly connect the arch to a battery, to cause a current in the arch.
Nothing will happen (but we have to check!).
Place a cylindrical magnet beneath the arch, and start and stop the
current.
Turn the magnet over, and see what effect this has.
Hold the magnet at other positions near the arch, and see when
the arch responds to the magnet and current.
Is there a difference between the first group of experiments (with
the compass) and the second set (with the foil arch), 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.
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.
2. Cut the aluminum foil into the shape of an arch.
With the arch lying flat on the table, tape the feet to the table, and then
bend the foil so that the arch stands up.
Attach wires the the feet, so that we can cause
a current to go over the arch.
Is there a difference between the first group of experiments (with
the compass) and the second set (with the foil arch), 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.