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The aim of the experiment 'resistance of a wire' is to find out whether certain variables affect the resistance of a wire. These are length of a wire, thickness, material, and temperature of the wire.

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Resistance of a Wire.

Aim: The aim of the experiment ‘resistance of a wire’ is to find out whether certain variables affect the resistance of a wire. These are length of a wire, thickness, material, and temperature of the wire. I also aim to calculate the length of unknown wires which I will place in the circuit, by measuring the resistance and plotting the results on my graph of end results.

Scientific Background: To calculate resistance we need to obtain potential difference and current through a circuit. The equation, once you have the relevant information, is:


Ohm’s law states that electrical current is directly proportional to potential difference. For different objects in a circuit there are different relationships between potential difference and current. Some of these are shown in a graph below.

The reason for resistance is the movement of free electrons. The number of free electrons depends on the material and the greater number of free electrons makes a material good conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor.

 The free electrons are given energy, so therefore they move and collide with other electrons near them. This happens across a length of a wire.

...read more.


Step Three

Place the crocodile clips at the 10cm mark on the metre ruler. Put the power pack on four volts and measure the current and potential difference.

Step Four

Do the same for all the rest of the measurements with a 10cm difference. Make sure the power pack is reset or turned on and off before each measurement is taken.

Step Five

Repeat the experiment two more times to assure it is a fair experiment. The length was the only variable that was changed and other variable remained constant.

Step Six

Put away all the apparatus.

...read more.


Step 2: Before starting the experiment make sure no outside light or any light from other sources can affect the LDR.

Step 3: Create a circuit with nichrome wire attached to the LDR and shine the torch on it for twenty seconds and measure the brightness of the LDR.

Step 4: Allow wire to cool sufficiently and redo the same two more times.

Step 5: Repeat the last two steps with the iron wire and then again with the copper wire.    

Step 6: Put away all the apparatus.

...read more.

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