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# Jerker: How Does a Magnet Produce Movement in a Current-Carrying Wire?

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Source:
Author: Janice VanCleave

### Problem

How does a magnet produce movement in a current-carrying wire?

### Materials

• 2 small disk magnets
• duct tape
• 18-inch (45-cm) wire (18-gauge with no insulation)
• pencil
• size D battery

### Procedure

1. Place the magnets on the edge of a wooden table, leaving a space of about inch (1 cm) between them. Make sure oppositely attracting magnetic poles (north and south) face each other.
2. Tape the magnets to the table.
3. Wrap the ends of the wire around a pencil, creating a loop and leaving about 4 inches (10 cm) at either end, as shown in the diagram.
4. Tape the wire to the pencil so that the ends are 2 inches (5 cm) apart
5. Place the pencil on the table so that the loop is centered between the magnets. Tape the pencil to the table.
6. Observe any movement in the wire loop as you simultaneously touch one end of the wire to the negative terminal of the battery and the other end of the wire to the positive terminal of the battery.
7. Immediately remove the wire from the battery.

### Results

The wire loop jerks either up or down.

### Why?

When an electrical current flows through a conductor, such as copper wire, a magnetic field is produced around the wire. H the current-carrying wire is placed in a magnetic field such as between the north and south poles of two magnets, the two magnetic fields oppose each other. The result is a force that tends to expel the wire out of the magnetic field between the two magnets. This movement is known as the motor effect.

### Let's Explore

1. Does the direction of the current affect the results? Repeat the experiment, this time reversing the direction of the battery terminals. Science Fair Hint: Electrons flow from the negative terminal end of the battery, through the wire, and back to the positive terminal of the battery. Draw diagrams showing the direction of the current Use arrows to indicate the movement of the wire. Include a legend for each part of the diagram, as shown in the figure on the next page.
2. What effect does the strength of the battery have on the results? Repeat the original experiment using two batteries. Use tape to connect the positive terminal of one battery against the negative terminal of the other battery.
3. What effect does the distance between the magnets have on the results? Repeat the original experiment twice, first increasing the distance between the magnets, and then decreasing the distance between the magnets.

### Show Time!

In the original experiment the north pole of one magnet facing the south pole of the second magnet. Construct an instrument that identifies the poles of the magnets by following these steps:

• Cut an L shape from a piece of stiff paper such as poster board. See the diagram for dimensions and labeling.
• Make a hole in the elbow of the L with a paper hole-punch.
• With the L facing up. insert the pencil point through the hole.

Hold the instrument over one of the diagrams showing current flow and movement of the wire. The pencil should point in the direction that the wire jerk—seither up or down. Rotate the instrument so the plus (+) sign lines up with the wire leading toward the positive terminal of the battery. The S on the instrument points toward the magnet, with its south pole facing the wire. The diagram shows the wire jerking up and the south pole of the magnet being identified.

### Check it Out!

Hans Christian Oersted (1777-1851), a Danish scientist, made a very important discovery while giving a lecture demonstration in 1820. Find out more about Oersted and the experiment that proved that an electrical current moving through a wire produces magnetism. You may wish to repeat Oersted's experiment and display diagrams of its results.