The essential components of electric heating elements are a battery, copper wire and Nochrome wire. Nochrome wire is the heating element used in toasters. Connecting the Nochrome to the battery runs an electric current through the Nochrome, which resists the current releasing heat. Lengthening the Nochrome reduces the heat produced; shortening the Nochrome increases the heat produced. Attaching a potentiometer to the circuit allows the operator of the heating element to control the temperature with a knob.
Connect the battery to the potentiometer. Use the copper wire to connect the positive (+) end of the battery to the "input" end of the potentiometer. Use another piece of copper wire to connect the "output" of the potentiometer to the negative (-) end of the battery.
Disconnect the circuit. Disconnect the copper wire from the "output" of the potentiometer.
Adjust the potentiometer to maximum resistance. There is usually a knob that controls resistance that the potentiometer produces. In some cases, a slider adjusts the potentiometer, which increases or decreases resistance when the operator moves it along a linear path.
Connect the Nichrome. Attach the Nichrome to the "output" of the potentiometer. Connect it to the copper wire that connects to the negative (-) end of the battery.
Adjust the potentiometer to reach the desired temperature. Lowering the resistance of the potentiometer will change the temperature of the Nichrome.
Adding copper wire between the potentiometer and the Nichrome will give the apparatus more flexibility (i.e., you can attach the heating element at a distance from the potentiometer).
Use heat resistant gloves, if you need to handle the Nichrome while it is connected to the circuit or while it is still hot after disconnecting. Do not attempt this experiment near water or flammable substances.