Oersted’s Experiment

Objectives

• Students explore the relationship between electricity and magnetism.

Materials

• Per Student:
  Pocket compass
  One-foot (30 cm) length of fairly thick wire, insulated or bare.
  1.5 volt electric cell (“battery”) of size “D” or “C”
  Sheet of paper

Key Questions

• What happens to the compass when the wire is connected to the battery?
• What happens to the compass when you change the direction of the electric current?
• How does the compass needle move when the compass is below the wire? Above the wire?

What To Do

1. Lay the compass on a table, face upwards. Wait until it points north.
2. Lay the middle of the wire above the compass needle, also in the north-south direction. You may lightly tape the wire to the table so that it stays put.
3. Connect one end of the wire to each end of the battery. Observe the compass. Did the needle move?
4. Quickly disconnect the wire from the battery. (It is not good for the battery to draw such a large current). What happens to the needle when you disconnect the wire?
5. Repeat with the connections of the battery reversed. In what direction does the needle move this time?
6. Take a piece of paper (5×10 cm) and fold the longer side into pleats (like a little accordion), about 1 cm high. Put the wire on the table, its middle in the North-South direction, put the pleated paper above it so that the wire is below one of the pleats, and place the compass on top of the pleats.
7. You can now repeat the experiment with the compass above the wire. What direction does the compass move in this time?