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Generator: Can a Magnet Produce an Electric Current?

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Author: Janice VanCleave

Problem

Can a magnet produce an electric current?

Materials

  • wire cutters
  • ruler
  • 2 7-yard (7-m) pieces of insulated 20-gauge or smaller wire
  • duct tape
  • quart (liter) jar
  • baby-food jar
  • compass
  • modeling clay
  • bar magnet
  • adult helper

Procedure

  1. Ask an adult to use the wire cutters to strip about 4 inches (10 cm) of insulation from the ends of each piece of wire.
  2. Coil one of the wires around the mouth of the quart (liter) jar. Twist the wire together to prevent it from unwinding, leaving about 18 inches (45 cm) of each end of the wire free. Tape the wire coil to the jar to prevent it from slipping.
  3. Coil the second wire around the mouth of the baby-food jar. Twist the wire together, leaving about 18 inches (45 cm) of each end of the wire free. Secure with tape.
  4. Place the larger jar on its side on a wooden table.
  5. Twist the bare wire from one jar to the bare wire from the other jar, forming two separated connections.
  6. Secure the compass inside the mouth of the larger jar with a small mound of clay.
  7. Turn the jar until the coils of wire line up with the compass needle, which points north. Use a small mound of clay to secure the jar to the table so that it does not move.
  8. Place the small jar as far apart as possible from the large jar.
  9. Ask a helper to dip one end of the magnet in and out of the mouth of the small jar while you watch the compass needle.

Results

The compass needle moves back and forth when the magnet is moved in and out of the jar.

Why?

The movement of a magnet inside the coils of wire generates an electric current. The electric current flows though the wire in one direction when the magnet is pushed into the coil, and in the opposite direction when the magnet is pulled out of the coil. This back and forth movement of an electric current in a conductor is called an alternating current. Since a magnetic field is produced around a current carrying wire, the magnetic field around the coil of wire circling the compass is what causes the compass needle to be deflected. The alternating current results in a change in the direction of the magnetic field around the wire, which results in the back-and-forth movement of the needle.

Generator

Let's Explore

  1. Does the strength of the magnet affect the amount of energy produced? Use a stronger magnet or make one by stacking round magnets with holes in their centers. Stick a pencil in the hole through the center of the magnets, and secure it with a piece of clay at the bottom of the stack. Hold the pencil to lower and raise the stack of magnets into the jar.
  2. Does changing the speed of the moving magnet affect the results? Repeat the original experiment, this time comparing the deflection of the compass needle when the magnet is moved slowly with the deflection when the magnet is moved quickly.
  3. Does the number of loops of wire through which the magnet moves affect the results? Repeat the original experiment twice, first using 5 yards (5 meters) of wire wrapped around the large jar, and then using 9 yards (9 meters) of wire.
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