### You can show how a current carrying wire will create a magnetic field surrounding it.

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Teachable Topics:

• Current flow
• Magnetism and magnetic fields

Theory:

When a current is sent through a wire, a magnetic field is induced in the area surrounding it. See, Current Carrying Wire and Induced Magnetism for how this magnetic field forms. Since the current is flowing in the same direction in both of the wires, the magnetic fields formed are in the same direction, causing the two wires to repel one another.

Apparatus:

• 2 wires approximately 30cm in length (insulated)
• 4 wires at least 1m in length (insulated)
• 2 sticks of wooden dowel (approximately 3cm in diameter)
• 4 glass rods (or any other sturdy, non-conducting material rods)
• 7ft. lab stand
• claw clamp and stand mount
• banana wires
• DC power supply with current control up to 10A.

Procedure:

• Put both of the wooden dowels into the claw clamp and mount the clamp onto the lab stand.
• Adjust the set up and the wires until the two 30cm wires are at the same height, parallel to the floor, straight, and parallel to each other.
• Attach the banana wires to the ends of the longer wires above the dowels so that the current is flowing through the shorter wires in opposite directions. See Fig. 1 for a schematic.
• Allow the apparatus to hang for at least 5 minutes or until it hangs stationary.
• Turn on the power supply and slowly turn up the current until the wires begin to attract one another.
• Only turn the current up to the wires' current limit.

SAFETY WARNINGS:

• If the wires begin to get hot, turn the current down immediately to avoid melting the wires.
• Do not run more than 10A through the circuit. If the current is raised to 10A, try and keep it there only for as long as necessary.