The Relationship Between Length, Width and Resistance of a Wire

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The Relationship Between Length, Width and Resistance of a Wire

Aim: To investigate how the length and width of a wire affects the

resistance of the wire.

What is resistance?

Electricity is conducted through a conductor, in this case wire, by

means of free electrons. The number of free electrons depends on the

material and more free electrons means a better conductor, i.e. gold

has less resistance. For example, gold has more free electrons than

iron and, as a result, it is a better conductor. The free electrons

are given energy and as a result, move and collide with neighbouring

free electrons. This happens across the length of the wire and thus

electricity is conducted. Resistance is the result of energy lost as

heat. It involves collisions between the free electrons, the fixed

particles of the metal, other free electrons and impurities. These

collisions convert some of the energy that the free electrons are

carrying into heat which means that electrical energy is lost.

Apparatus: I will be using: - An Ammeter

- Voltmeter

- Variable resistor

- Power Supply

- Various diameters of wire

- Crocodile clips

- Metre ruler



Secondary Source - (Obtained in A-level PHYSICS by Roger Muncaster.

Page 536.)

The electrical resistivity of a material is defined by



· R = Resistance of some conductor(Ω)

· L = Length of the conductor(m)

· A = Area of cross - section of the conductor (m²)

· Ï = the resistivity of the material of which the conductor is made


The experimental determination of the resistivity of a material

involves measuring the resistance of a specimen of the material. The

specimen must be regularly shaped in the form of a wire; its diameter

should be measured at six different points.

Variables and Controls:

The variables that I will be using are the length and diameter of the


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