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# What determines the resistance of a metallic conductor? Investigate a physical factor that will affect resistance of a piece of Constantan/Nichrome wire.

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Introduction

GCSE Physics Investigation

Problem:

What determines the resistance of a metallic conductor? Investigate a physical factor that will affect resistance of a piece of Constantan/Nichrome wire.

Possible Variables to be investigated:

Current, Temperature of wire, Length of wire and thickness of wire

Independent Variables:

This is the variable that I will change. It will be the length of wire.

Dependant Variable:

This is the variable that I will measure. This will be voltage so I can work out the resistance using ohm’s law equation, Voltage (V) = Current (I) x Resistance(R) I will rearrange this equation to Resistance (R) = Voltage (V) / Current (I)

Controlled Variables:

These are the variables that will stay the same. They are Current, Temperature of wire and thickness of wire.

Background Knowledge:

Resistance is a force, which 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.

George Ohm discovered that the emf of a circuit is directly proportional to the current flowing through the circuit.

Middle

Predicted graph:

Safety Precautions:

There are not many safety precautions that need to be taken into consideration, in this experiment. The main two I can think of are stated below:

Do not carry out the experiment in wet areas, as water is a very good conductor, and thus could be very dangerous.
Do not touch the wire when the power pack is switched on, because the current would heat up the wire.

Diagram of Apparatus:

Voltmeter                                                                                                                       Power pack
Nichrome wire
Meter Ruler                                                                                                             Crocodile Clips

I set up my experiment as shown above.

I started the experiment by attaching the Nichrome Wire (over 80cm long) to the meter ruler then cut to size. Then the power pack was switched on which was connected to the Nichrome wire via the crocodile clips. The resistance was then recorded down for various lengths ranging from 20cm to 80cm. I recorded each in a table.

To collect the data for my graph I had chosen to take a range of 7 lengths. I had chosen a range of 7 as to plot an accurate graph I will need at least 7 points to mark on the graph.

Conclusion

C = A - B

A = overall resistance of Nichrome wire, crocodile clips and connecting leads
B = overall resistance of crocodile clips and connecting leads
C= resistance of Nichrome wire

I also found that the experiment was quite easy to set up, as it was simple and uncomplicated.

Further experiments I could do related to the resistance in a wire, would be to see whether the following factors would make a difference in the resistance of a wire: (I have made a prediction for each factor from my own scientific knowledge on how I think the resistance would change in a wire for that particular factor)

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.

Stuart Mc Gaffin

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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