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To investigate the effect of length of a wire and cross sectional area on the resistance

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Introduction

To investigate the effect of length of a wire and cross sectional area on the resistance

I will test different lengths and areas of wire and observe and record the resistance. I will see how these variables affect resistance, which length or area of wire gives the least resistance and which gives the most. In my preliminary experiment I will vary the length of the wire I use. By varying the length I

Scientific 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.

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Middle

Therefore voltage measures the amount of energy used up in getting each coulomb of charge through a wire. The units for voltage are the same as joules per coulomb.

A metal wire can conduct electricity because the outer electrons of the atom are free to carry a charge. An electron is part of an atom with a negative charge and almost no mass. The more free electrons a metal has the better conductor it is.

Predictions

Resistance/Length

I think that as the length of Nichrome wire increases so will the resistance. As the length of Constantan wire increases so will the resistance. If the length of the wire is doubled the resistance will double.

Resistance/Area

I think that as the area of Constantan and Nichrome wires increase the resistance will decrease.

Fair Test

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Conclusion

The area of Constantan and Nichrome wire needs to be kept constant for my first experiment (though it will be varied for the second). This is because the larger the area the more current can pass through, giving a smaller resistance.

-The length of the two wires

The length of Constantan and Nichrome need to be kept constant for my second experiment (though it will be varied for the first). This is because the longer the wire the more times the free electrons will collide with other free electrons and any other impurities in the metal, increasing the resistance.

I shall take repeat readings.

Electrical Safety

In order to keep my experiment safe I shall need to take into account electrical safety. No water is to come near the circuit therefore my hands are to always be dry. I shall disconnect the circuit in between each reading to prevent the equipment overheating which could damage my experiment

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