Monday, 20 May 2013

Resistance - factors affecting resistance

The following practical set up will allow you to test a number of factors affecting resistance.

When finding the resistance of a wire you will need to measure the current passing through the wire and the voltage across it. Ammeters are connected in series and voltmeters are connected in parallel across the test wire.

A circuit should be set up as shown below, with the wire being tested connected between the circular terminals on the diagram, which should be crocodile clips or points on a breadboard.



To fully investigate the factors affecting the resistance of a wire you should first choose a fixed length and material for the wire. You may then investigate how the area of the cross-section of the wire affects the resistance.

Once you have recorded values of current and resistance for different thickness wires select one thickness and alter the length placed between the crocodile clips.

To find the resistance you will need to use the equation V / I = R with the readings on the Ammeter and Voltmeter.

You may need to do a little preliminary testing as, depending on your power supply,  a wire which is too short or too thin may melt.

Once you have collected your data you should plot graphs of area vs resistance and length vs resistance.