Investigate how the length of a wire affects its resistance.

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GCSE Physics coursework

Resistance of a wire Coursework

Plan

Aim

To investigate how the length of a wire affects its resistance.

Theory

A current is a flow of charge. Electric current is the flow of electrons, usually in a wire. A current comes from cells or batteries, the electrons are already in the wire but have no charge.  Current is measured in Amps using an Ammeter. The Ammeter must be placed in series with any components because it measured the current passing through it.

        

To make a current flow you need a voltage. A cell or battery provides voltage. It is the energy that is needed to move a certain amount of charge (electrons) between two places. Voltage is measured in volts using a voltmeter. The voltmeter must be placed parallel to components because it is measuring the energy the electrons use up as they pass through the component.

Electrical resistance is the effect a wire or component has on a current as it tries to prevent the current flowing through it. The electrons in a wire flow through the wire but there is a chance that they will collide and be slowed down by an atomic nuclei, this is resistance.

The resistance of a length of wire is calculated by measuring the current present in the circuit (in series) and the voltage across the wire (in parallel). These measurements are then applied to this formula:

 

V = I/R                    

Where V = Voltage, I = Current and R = Resistance

 

This can be rearranged to:

 

            R = V/I                 

This formula only works for objects at a constant temperature.

         

   = Nucleus

        = Electrons (current)

 

The diagram above shows electrical resistance.

Variables 

  • Type of wire- the arrangement of the nuclei in the wire can make a collision more or less likely depending on density on the wire.
  • Temperature- when a nucleus gets hot it will vibrate therefore taking up more space and making a collision more likely.
  • Width of wire - In a wider wire there is more space between each nuclei, providing the electrons with more space so a collision is less likely reducing the resistance of the wire.
  • Length - I aim to find out whether or not the length of the wire makes a difference.
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Hypothesis

When the length of wire is increased the resistance also increases. When the length of the wire is decreased the resistance of the wire in decreased. I think this because the longer the wire is the more nuclei there is for the electrons to bump into, therefore making their path more difficult.

I

Preliminary Test

I need to find a safe voltage, which also gives good, usable results.

 

In the lab ...

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