Resistance in Nichrome Wire.

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Renny Popoola 11d

Resistance in Nichrome Wire

Aim: To investigate the resistance of Nichrome wire. To find out how the length of a wire affects its resistance.

Plan: 

Background information: Resistance is the force, which opposes the flow of electric current round a circuit so that energy is required to push the charged particles round 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. Resistance is measured in Ohms (~). A resistor has a resistance of one ohm if a voltage of one volt is required to push a current of one amp through it. The total resistance of resistors in series is the sum of the resistance of each one.

George Ohm discovered that the electromotive force or potential difference of a circuit is directly proportionate to the current flowing throughout the circuit. He also discovered that a circuit sometimes resisted the flow of electricity. He then came up with a rule for working out resistance.  Resistance is equals to Voltage divided by current and the formula could be written like this:

This also tells us how to work out the current and voltage using other information. Therefore if I have a voltage of 6 volts and a current of 2 amps, my resistance will be 3 ohms.

Resistance is shown to depend on the type of metal. The metal is shown to be a lattice of positive metal ions surrounded by a sea of free electrons. One reason why different metals do not have the same resistance is that they contain a different number of free electrons. There are other reasons, such that the positive ions vibrate with different amplitude or frequency for different metals.

Resistance is proportional to the length of the wire – doubling the length doubles the resistance.

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Resistance also depends on the thickness of the wire. It is actually inversely proportional to the cross-sectional area of the wire: as the area doubles the resistance halves. This is demonstrated by using two wires to double the area (doubling the diameter of a circular cross-section wire would give four times the area and so one quarter of the resistance).

Equipment:                                                                             ...

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