Effect of temperature on conductivity and resistance
The materials required for this science fair project:
- 5 meters of varnish insulated copper wire with diameter 0.5mm (may be purchased from hobby stores, motor rewinding workshops, etc...)
- A PVC pipe about 300mm in length
- Three 1.5V batteries and a casing to hold the batteries
- 3 jumper wires with crocodile clips at both ends
- An ohm meter
- An ammeter that can measure current up to 10A
- A paper knife
- An infrared thermometer
- 1 roll of insulation tape
1. For this experiment, the independent variable is the temperature of the copper wire. The dependent variable is the resistance of the wire. This is determined by measuring the current and resistance of the wire. The constants (control variables) are the room temperature, the applied voltage, the diameter of the wire and the length of the wire.
2. The wire of ? 0.5mm and length of 5 meter is wound around the PVC pipe. The ends of the wire are fixed to the pipe using the insulation tape. About 3 cm of insulation is removed from the wire tips using the paper knife. The resistance of the wire is measured using the ohm meter.
3. The 3 batteries are connected in series to produce 4.5V. The ammeter, battery and wire wound around the pipe are connected as shown in figure 1. Connection is done using the jumper wires.
4. The initial current reading shown on the ammeter is recorded in the table below. As the current flows in the magnet wire, the temperature of the wire will increase. This temperature is measured using the infrared thermometer. As the temperature increases 10°C, the ammeter reading is recorded, and the wire is disconnected from the circuit and the wire resistance is immediately measured using the ohm meter.
5. The procedure 4 is repeated when the temperature of the wire increases every 10°C until the highest temperature reached and the measurements are recorded in the table below.
Be careful when handling electric cables and knives. Adult supervision recommended.