... The amount of slowing that occurs as electrons pass through an object is the amount of electrical resistance. The greater the resistance, the lower the current that is able to pass through the wire. ... Resistivity is the power of resistance. ... The power or property of resistance
2. Also called specific resistance. ... the resistance between opposite faces of a one-centimetre cube of a given material; ratio of electric intensity to cross-sectional area; reciprocal of conductivity.
Many variables can affect the resistance of a wire. These include
v Thickness – a thick wire will allow more current through and so it has a lower resistance.
v Temperature – heat increases the kinetic energy of particles in the wire meaning the particles inside collide more resulting in a higher resistance.
v Length – As the wire length increases, the current has further to travel and so the resistance increases. This is due to the number of particles in the wire which the electrons collide with.
v Type of wire – Different types of wire have different resistances. ...
Resistance is measured in Ohms and can be found using Ohm’s Law. In Ohm’s Law, the potential difference measured in volts is divided by the current, measured in amps, to find the resistance, measured in Ohms . Therefore R=V
I
During this experiment, I will vary the length so the other variables must be controlled to make the experiment fair. To do this, our experiment will be carried out at room temperature with the same person taking the readings and using only one type of wire – nichrome wire. The thickness of the wire will be measured using a micrometer at regular intervals and a large protective resistor will be placed in the circuit to prevent the nichrome wire from overheating.
Pilot Test
I will take two pieces of Nichrome wire, one thick and one thin. ... From this I will calculate the Resistance using Ohm’s Law (R = V). I will then decide which wire has the greatest range of results.
I
In this preliminary experiment, I will choose which wire to conduct my experiment with. ... I have measured the length in centimetres, the potential difference in volts and the resistance in ohms for each table.
Using the thin nichrome wire
Using the thick nichrome wire
As it shows a greater variety of results, I have chosen to use the thin nichrome wire in this experiment.
Method
I will take 80 centimetres of thin nichrome wire and set this up in the circuit shown in the pilot test with the crocodile clip as close as possible to the end of the wire. ... I will switch the power pack off between readings to keep the temperature lower as the temperature in the circuit will also affect the resistance.
Using these readings, I will calculate the resistance at each length along the wire. To do this, I shall divide the potential difference recorded at every stage by the corresponding current to find three resistances (measured in ohms) at each length. I will then determine the average resistance for each of the 8 lengths measured by adding the three resistance totals together and dividing the sum by 3.
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