Investigation to determine how the value of resistance of a resistance wire changes with it's length.
The wires used in electrical circuits tend to resist the movement of electrons in it. We say that the wire has a certain resistance to the current. The greater the resistance of the wire is, the more voltage is needed to push a current through the wire. There are four factors which could affect the resistance of a wire. .
1. The length of the wire.
2. The size of the cross-sectional area.
3. The substance of the wire.
4. The temperature.
The aim of this experiment will be to investigate how the value of a resistance of a resistance wire changes with it's length. To calculate the value of resistance of a resistance wire, the following formula is used;.
Resistance = Potential Difference (in V).
Current (in A).
The resistance will be calculated in Ohms, the potential difference in volts, and the current in amps.
Plan.
Apparatus too be used:.
1. Power Pack (used to control the flow of electron through the circuit).
2. Amp metre.
3. Voltmeter (used to calculate the value of resistance).
4. Resistance wire (the length of which will be used to change the amount of resistance).
5. Crocodile clips.
6. Wire (used to make the circuit).
Safety Precautions.
As in all scientific experiments, safety is a large issue and will be so throughout the experiment. Ties should be tucked into the shirt and the hair should be tied back. The experiment should be kept well away from water other school equipment. All main should sources of power should remain switched off when they are not in use.
Fair Test Procedures.
1. The same power pack should be used throughout the experiment.
2. The test should be carried out under the same conditions, under the same temperature. (ie room temperature).
3. The lengths of resistance wire should be taken from the same piece of resistance wire, ensuring that the cross-sectional area is the same throughout.
4. The results from the volt and amp metres will be left for a few seconds, and then recorded to ensure that they are accurate.
