Electricity & Magnetism: How Resistance Produces Heat

[embed]https://www.youtube.com/watch?v=og3JjfpgHpo[/embed]

(ADULT SUPERVISION REQUIRED)

This experiment will allow you to see how heat is produced by the resistance in an electrical conduit.

MATERIALS:

• Insulated wire with alligator clips
• 9-Volt Battery
• Nichrome Wire
• Candle
• Piece of Wood (150mm x 50mm x 20mm)
• Wire Cutters
• Hammer & Nails

METHOD: When electricity passes through wire it produces heat, which can be very useful in light bulbs, electrical heaters or even toasters. The reason the heat builds up is due to ‘resistance’ in an electrical conduit. While this is useful in some applications, it can also be very undesirable in motors or television sets if too much heat is produced. The heating elements in toasters are made of ‘nichrome’ which is a high resistance material. Nichrome is made of iron, chromium and nickel and is used in these application because of its high electrical resistance and ability to heat up very quickly. This experiment will allow you to pass electrical current through a wire (nichrome) to test which side of a battery heats up first, the negative or positive terminal. Follow these steps to begin:

1. Hammer a nail partway into each end of the flat piece of wood. This will form the base and the two nails will form the terminals that will be attached to the nichrome wire.
2. Take a piece of nichrome wire (which can be obtained from an old toaster), wrap each end around the head of both nails, making sure the wire is slightly taut and level between both nails.
3. With the help of an adult, drip a thin coat of wax from a lit candle onto the entire length of the nichrome wire. (You may want to use old newspaper to catch any wax that may spill.)
4. Using the insulated wire, connect one piece to the negative terminal of the battery connecting to a nail, and then to the positive terminal of the battery to the second nail.
5. Watch what happens! You will notice that the wax coating near the nail connecting to the negative battery terminal starts to melt faster than the wax on the opposite end.

WHAT WE HAVE LEARNED: Electricity moves or ‘flows’ through different materials faster than others. Resistance, measured in ‘ohms’ is the measurement of how well or how poor a material conducts electricity. The resistance in wire is determined by length or thickness of the wire and its material. Electrical current resistance causes friction which produces heat. Higher resistance will produce more heat. Electricity (electrons) flow from the negative terminal of a battery and this has an excess amount of electrons, while the positive terminal of the battery lacks electrons. This experiment shows us that electrical current passing through a nichrome wire coated with wax will heat the negative terminal first due to the resistance and electron build up which want to pass through the wire to the positive terminal. TERMS TO UNDERSTAND: Resistance: Any material’s opposition to the flow of electric current and resistance is measured in Ohms. Electrons: Tiny particles with a negative charge capable of creating an electrical current. In Series: Connected one after another or in a chain rather than parallel.