To investigate how the electrical resistance of a wire changes in relationship to its length.

Apparatus:

• Lab pack
• Wires
• Ammeter
• Voltmeter
• Crocodile clips
• Wires to test (different lengths)
• 1000ml Boiling jug

Diagram:

Physics coursework

Method:

1. Set up apparatus as diagram shows on previous page.
2. I connected a wire with the thickness of 0.56 mm and a length of 600mm (to start with) to the crocodile clips to the ends of the wire.
3. I put the wire in the water.
4. I then switched the voltage around from 0 to 15 on the lab pack to give me a measurement in amps which gave me my current.
5. I repeated this with the same thickness of wire but different lengths of 600mm, 500mm, 400mm, 300mm, and 200mm.
6. I recorded my results in a table and drew a graph of my results.

Variables:

• I will keep the thickness of the wire the same in every experiment.
• In every experiment I will use a new bit of wire.
• Only nichrome wire will be used.
• My 1 litre jug of water will be kept at a constant temperature throughout the experiment.

Theory:

Ohms law.

Formula for resistance is; R=V

                             I

Ohms Law is a mathematical equation that shows the relationship between Voltage, Current and Resistance in an electrical circuit.  Ohms are equal to the potential difference, in volts divided by the current, in amperes. As the length of the wire is increased the number of collisions the current carrying charged particles make, with fixed particles also increases and so the value for the resistance of the wire becomes higher.