Perform an experiment involving investigation into the resistance of a wire.

• Varying length – as the length increases, the resistance increases.
• Varying cross sectional area – as the cross sectional area increases, the resistance decreases.
• Changing the substance – e.g. copper is a good conductor and is used for connecting wires.  Nichrome has more resistance and is used in the heating elements of electric fires.
• Temperature – as the temperature increases, the resistance of the wire increases.

I will be investigating two of these factors.  I will be changing the length and the cross sectional area of the wire.  I will use nichrome wire throughout the experiment.

I am going to use a metre length of wire attached with sellotape at both ends to a metre stick.  Using two wires and a battery pack I am going to run a current through the wire at various lengths starting at 10cm and continuing at 10cm intervals.  I will do this by keeping one wire at 0cm, and placing the other one at points along the wire.  I will use a voltmeter and an ammeter to measure the voltage and the current.  After gaining these results I will calculate the resistance and observe how it changes as the length of the wire increases.

In order to gain a wide range of results I will perform three separate experiments changing the SWG (standard wire gauge) of the wire and the output (volts) of the battery pack.  My three sets of results will be:

SWG 32 – 4 volts

SWG 32 – 3 volts

SWG 24 – 3 volts

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Equipment

2 metres SWG 32

1 metre SWG 24

metre stick

battery pack

2 connecting wires

ammeter

voltmeter

sellotape

Diagram

Safety

In order to make sure this experiment is safe I will not use an output greater than 4 volts and make sure there is not a current running through the wire for too long; otherwise the wire will overheat.

Fair testing

I will keep this experiment fair by only changing one variable at a time, i.e., either the SWG or the output.  I will use the same output when completing a single set of results where possible.

Prediction

I predict that the longer the wire the greater the resistance.  This is because there are more electrons creating obstruction for the current as the length of the wire increases.