EXPERIMENT TO FIND THE AFFECT THAT THE LENGTH OF A WIRE HAS ON ITS RESISTANCE
The aim of this investigation is to find out how the resistance of a wire is affected by its lengths. I will do this by changing its lengths and working out each lengths potential difference and current. The reason that I am measuring the potential difference and the current of the circuit is because the formula for resistance is.
(resistance= ohms (Ω), potential difference= volts (V), current= amperes (A))
Electricity is the movement of charged electrons inside an insulator and it is also a form of energy. The constant variables in this experiment will be:
- The temperature: the hotter the inside of a metal the more active the electrons are and the more collisions they will make with the walls of the wires making it harder for the current to pass though
- The material of the wire: different metals have different resistances and will give you unreliable results
- The thickness of the wire: the thinner the wires are the less current can pass through it at one time.
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The independent variable will be the length of the wires as we are trying to find out its affects on the resistance. The independent variable affects the dependant variable as in that when you change the independent variable the value of the dependant variable will change. The dependant variable in this case would be the resistance of the wires and it will change as the length of the wire changes.
Hypothesis: I think that the resistance of the wire will be higher when it is longer. This is because the electrons have further to travel than inside the smaller wires so it is harder for them. Therefore the electrons will use up the energy they obtained from the power source quicker and lowering the potential difference.
- Nichrome (nickel-chromium alloy) resistant wires with changeable lengths
- At least 5 conducting wires- to connect all the components
- Voltmeter- to measure the potential difference
- Ammeter- to measure the current
- 2V battery- to provide sufficient voltage to push the electrons around the circuit. Converts AC to DC and steps it down to 2V from 230V
- Access to mains electricity-to power the power source
Firstly place two wires into the power source and connect one of them to the first opening of the nichrome wire. Connect the other end to an ammeter. Connect the ammeter and the smallest chosen length of your nichrome wire together to complete the circuit.
After this you have to place the voltmeter in series with the nichrome wire so that it can measure the potential difference. The wires should have and opening at the top of where the wire is plugged in. You need to connect two wires to the volt meter and plug them both into the openings of the wires in the nichrome resistant wires. And repeat this for each of the lengths you have chosen to record results for.
If you want to add another independent variable then you have to change the thickness of the wire and see its affects on its resistance. You can change the temperature of the wires to see its affect on resistance. You can change the material of the wire as it wil differ from the nichrome or you can change the battery to see if it has any affect on the voltage.
The graphs show a strong positive correlation between the length of the wire and its affect on the resistance. This occurs in every repeat of the test so the results can be counted as mostly reliable. There is one outlier; I believe this is down to a surge in voltage which is probably because we did not allow enough time for the circuit to cool down after the previous measurement.
My hypothesis was proved true by my investigation as the resistance increased with the length of the wire. This means that the electrons found it harder to travel across longer lengths therefore needing more voltage to push it along. This means there is an increase in voltage and decrease in the current. The resistance equation mans that the resistance will keep getting higher with the length of the wire.
If I were to do this experiment again I would change a few aspects of it in order to obtain more reliable results and to make it a fairer test. I would keep the current the same although out the experiment by using a rheostat and adjusting the current to the same before every measurement is taken. I would keep the temperature of the room the same so that it does not have any effect on the electrons or the conducting wires. This will make it’s a fairer test because then you are only having one dependant variable which will make the outcome of the dependant variable more reliable.