Investigating (one of) the factors that affect resistance.

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Caroline Morris        Physics Coursework        

Investigating (one of) the factors that affect resistance

Resistance is the property of an electrical conductor, to work against the flow of the current and change some of the electrical energy into heat. According to Ohm's law the quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit. The standard abbreviation for electric resistance is R and the symbol for ohms in electric circuits is the Greek letter omega, Ω. For certain electrical calculations, it is convenient to employ the reciprocal of resistance, 1/R, which is termed conductance, G. The unit of conductance is the mho (ohm spelled backwards) and the symbol is an inverted omega, W. To find resistance we use the equation

Resistance = Voltage / Current is used.

The resistance of an object is determined by a property of the substance of which it is made of, known as the resistivity and by the length and cross-sectional area of the object. Also other variables such as the temperature can determine the resistance. Usually, a material's resistance increases with the rise in temperature as the voltage going across the wire has to avoid the resistor's atoms more. This produces more energy causing plenty of heat.

 The variable which I will be changing, length of the wire will make a difference because there will be more atoms for the current to pass through so there will be more resistance in the wire. The diameter of the wire will make a difference as the thicker the wire, the easier the current will be able to pass through it, as there is more room within the wire. The material the resistor is made out of will also make a difference as if the wire has a high density, there will be more atoms in the wire causing high resistance, but if the wire has a low density, the atoms are less so there are so the is less resistance. The temperature will make a difference as if the temperature is high, there will be plenty of kinetic energy in the resistor and the atoms will be moving about. The current will find it hard to pass through the wire with atoms moving about so there will be more resistance. For the experiment, the variables except the length will be kept the same, as it will make it a fair test.

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I am going to investigate how much changing the length of a wire affects the resistance in a circuit. I am going to test this by changing the length of a wire in a circuit, in steps of 10cm. I will record the readings of the volts and currents in a table. By recording these readings I am then able to work out the resistance. By using the formula.       V

            R =  

                     I

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