Resistance of a Wire

Resistance of a Wire

Aim

The aim of this investigation is to find out the cross-sectional area

of a wire affects its resistance.

Diagram

Equipment

· Voltmeter

· Ammeter

· 100 cm resistance wire (variable thickness)

· Power pack

· Micrometer

· Crocodile clips

· Meter ruler

Method

· Set up the circuit as the diagram above shows with the smallest

thickness of wire first.

· Set the voltage on the power pack to 6V.

· Record the actual voltage supplied and the current in the circuit.

· Change the thickness of the wire to the next thickest.

· Repeat until all the wires current and voltage has been recorded.

· Draw a graph of resistance against the cross-sectional.

Safety

Keep the voltage low or it will heat up and the wire will melt which

may lead to someone burning themselves. Use a reasonably long length

of wire so that the current does not get too high and melt the wire.

When removing the wire make sure that the power pack is turned off so

that you do not get electrocuted. Also wait for the wire to cool down

before you remove it so as not to burn yourself. If the wire does

start to melt maybe decrease the amount of current going through it.

Fair test

For any fair test only one of the variables should be able to change.

These are the variables:

1. Length of wire: This may change the resistance of the wire as the

electrons have further to travel so there will be more collisions

therefore more resistance.

2. Material of the wire: According to Ohm's Law; the resistance of a

metallic conductor is constant as long as the temperature stays the

same.

3. Temperature: This may change the resistance of the wire because the

hotter the wire gets the electrons move around more and so the more

collisions there are therefore the more resistance there is.