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Nichrome Wire Experiment

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Physics Coursework

Nichrome Wire Experiment


              What determines the resistance of a metallic (wire) conductor?

Possible variables to be investigated

  1. Length of wire.
  2. Thickness of wire.
  3. Amount of current passing through the wire.
  4. Temperature of the wire.
  5. The material of the wire.
  6. The amount of voltage passing through the wire.

Title of investigation

                                     An investigation into how the length affects the resistance of a piece of Constantan/Nichrome wire.

Independent Variable

                                     The length of the wire.

Dependant Variable

We will use Voltage to measure the resistance of the wire using Ohm’s law.

Constant Variable

  1. Current passing through the wire
  2. Material of the wire
  3. Temperature of he wire
  4. Thickness of the wire

Background Knowledge

In looking at resistance, we must take a number of other topics into consideration.  Resistance is a force that opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. E.g. the filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow.
Resistance is measured in ohms.  The current is the flow of free electrons through the circuit, and the voltage is the driving force that pushes the current around the circuit.  

George Ohm discovered that the voltage of a circuit is directly proportional to the current flowing through the circuit, in certain circuits. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit:

V/I = R

V - Volts

...read more.


Here is table of results that I will record my results in.  I will have 3 tables of results, one for each current.

Length of wire (cm)

Voltage (V)

Resistance (Ohms)










Fair Test

To ensure that I am conducting a fair test, I have decided to take a number of measures to ensure that this occurs.  I am going to use a ruler to measure the Nichrome wire and ensure that it is the correct length.  I am also going to try and ensure that the current is within 0.01Amps of the desired current.  I will also ensure that the thickness of the wire stays constant for each length and current.  I will also make sure that I am using the same wire for each length, as a different wire might cause distortion of results.  I shall also ensure that the designated current passing through the wire will not change until all the lengths of wire have been tested and the voltages recorded, then shall we increase/decrease the current to the desired figure.  I will also try and use the same equipment for each current because any change of equipment might cause a distortion of results.  

Safety Considerations    

In doing this experiment, we must take many safety considerations into hand.  We must try to keep the current low enough to avoid the heating effect, which may burn us or cause damage to surrounding objects.  We must also not touch the wire once the power pack is turned on, because we do not know if the wire is hot or not.

...read more.


I could now carry out further experiments related to the resistance in a wire and see if the following factors would make any difference in the resistance of a wire.

Wire width: I think that if the wire width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.

Temperature: I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.

Material: I think that the type of material of the wire will affect the amount of free electrons, which are able to flow through that wire. This is because the number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase

...read more.

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