Resistance of a nichrome wire.

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                                                   Resistance of a nichrome wire.

Aim

My aim is to investigate some of the factors of the resistance of metal wires.

The scientific theory for this experiment is based on ohms law, using ohms law I will find what affects resistance when there are different currents flowing through it.

Hypothesis

The longer the wire the more resistance than the short thick wire of the same material. Sliver is the best conductor, but copper, the next best conductor is cheaper and is used

For connecting wires and is used in electric cables.                  

When a high resistance is required e.g., to reduce the current in a circuit special alloys are used. The most common of these are constantan (called coutro or eureka) maganin and nichrome. Constantan is used for general purpose, while maganin is used for making high quality standard resistors. Nichrome is alloy from which elements of electric fires are made, since it resists oxidation when red hot. Constan and maganin wires have a resistance of twenty five times and nichrome about sixty times, that of a copper wire. This is my hypothesis for my investigation.

Prediction.

 I predict that the longer the wire the higher the resistance will be. I used my scientific theory to make my prediction.

Scientific theory

Ohms law.

In 1826, George Simon Ohm, a teacher of physics Cologne, published a book containing details of some experiments he had made to investigate the relationship between the current passing through the wire and the potential difference between the ends of the wire. As a result of his experiment he stated that: the current passing through a wire at a constant temperature is proportional to the potential difference between the ends.

 A conductor for which this relationship is true is said to be obeyed by ohms law. This law may be expressed as;

                            Potential difference = constant

                                     Current

 For a given potential difference, a high resistance will pass a small current and a low resistance will pass a large current. There for the value of the constant in the above equation which is high when the current value is small and low when the current value is large can be used to measure the resistance of a wire.

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       There for it can also be written as:

                                  Potential difference = resistance

                                           Current

In other words the resistance of a conductor is the ratio of the potential difference (pd) across it the current flowing through it.

The units for the p.d are volts and current as amperes.  The definition above helps to find the unit of electric resistance. ...

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