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Resistance of a wire

Extracts from this document...


Investigation to see how Length Affects Resistance in Wires


Physics Coursework


GCSE Physics Coursework

Background Knowledge

What is Resistance?

Electrical resistance is the property of any object or substance of resisting or opposing the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit.

The resistance of an object is determined by a property of the substance of which it is composed, known as the resistivity, and by the length and cross-sectional area of the object, and by the temperature. At a given temperature, the resistance is proportional to the object's resistivity and length, and inversely proportional to its cross-sectional area. Usually, a material's resistance increases with increases in temperature.

In terms of the atoms within the wire resistance is the amount of obstacles that hinder the movement of charged particles through a wire. As a particle is passing through a wire it is constantly ‘crashing’ into atoms and therefore being hindered from moving. The more times these particles are hindered by obstacles, the more ‘resistance’ a wire has.

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Ammeter – the ammeter is used to measure the current across a circuit

Voltmeter – very much like the ammeter, this measures voltage

Variable Rheostat – by sliding the bar one can change the resistance of a circuit

Ruler – this will help in measuring the distance between crocodile clips and also provide a non – conductive surface for the wire

Crocodile Clips – the clips will help attach the wire to the rest of the circuit

Leads – these will be required for attaching different components to the circuit


I think that the longer the wire, the more resistance, as preliminary results would suggest this. This would be as electrons lose some of there energy when they collide.

I predict my results will be like this:



I also predict that:

  • The graph will be a straight line through the origin, because current is proportional to the voltage, hence the resistance (R=I/V) is constant.
  • I predict that resistance will be proportional to length; this is because I believe that a length of wire 10cm long will have twice as many collisions as that of a wire 5cm long.
  • I believe that, along with my research, that an increase in current will come a decrease in resistance.

Collecting My Data

As mentioned above, I will be collecting data in order to discover how the length of a wire affects resistance. I have decided to use this as a variable as it is the easiest to maintain. Area and temperature require much more preparation and specialized apparatus.

Whilst conducting my experiment, there are a number of safety issues that I will have to address in order to ensure the safety of myself and others:

  • When working at high voltages, the wire may become hot. If it turns red it all power must be switched off and the wire left to cool.
  • If the wire is left to heat on a bench it could burn it and produce fumes. Whilst experimenting on wires they must be securely attached to the ruler.
  • If fumes are created I must wear goggles and keep windows open.
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After discussing my results in the above conclusion I have decided that the conduction of my experiment went well, and that I collected a good enough set of results in order to make a valid conclusion.

It may however be beneficial to conduct another set of experiments in order to further my knowledge. Further experiments could include investigations that use different constants such as:

  • Varying the diameter; through varying the diameter I should find that the resistance is lower as there is more room for the atoms to move.

  • Temperature; as the temperature rises, the resistance should change as the atoms are receiving more energy and moving more.

  • Material of the wire; different materials have different properties which could affect the resistance.

Conducting these experiments and then comparing the results could prove my predictions further.




Ben Ingram        10R        Page  of

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