Investigating an Electric Generator
All generators have two main parts— a magnet and a wire that is wrapped into a coil. The arrangement of these parts varies, depending on the size and power of the generator and whether it produces direct or alternating current. In this lab, you will determine how several variables affect the current produced by a simple generator.
Problem How do the direction in which the magnet moves and the number and direction of the turns in the coil affect the current that a generator produces?
Materials
cardboard tube
5-m length of insulated wire
metric ruler
multimeter
bar magnet
graph paper
For the probeware version of this lab, see the Probeware Lab Manual, Lab 9.
Skills Observing, Using Graphs
Procedure
Part A: Changing the Number of Turns
On a separate sheet of paper, make a copy of the data table shown below.
Slip the wire between your hand and the cardboard tube so that 15 cm of wire extends from the tube. Use your other hand to wrap the long end of the wire around the tube 10 times in a clockwise direction. Make sure all the turns are within 10 cm of the end of the tube. CAUTION Be careful not to cut yourself on the sharp ends of the wire.
Connect both ends of the wire to the multimeter. Set the multimeter to measure current.
Hold the bar magnet by its south pole. Observe the multimeter as you quickly insert the bar magnet into the open end of the cardboard tube that is wrapped with the wire coil. Repeat this step if necessary as you adjust the scale of the multimeter. Record the maximum current in your data table.
Disconnect the multimeter from the end of the wire that is farther from the turns.
g Record your prediction of how increasing the number of turns in the coil will affect the current.
To test your prediction, wrap the wire around the end of the tube 10 more times in the same direction as you did previously—clockwise. You should now have a total of 20 turns. Reconnect the wire to the multimeter.
Repeat Step 4.
Again, disconnect the multimeter from the same end of the wire. Wrap the wire clockwise around the tube 10 more times for a total of 30 turns. Reconnect the wire to the multimeter.
Repeat Step 4 and then disconnect the multimeter from the same end of the wire.