The aim of this experiment is to find out what factors affect the resistance of a wire in a circuit.

Plan

Aim: The aim of this experiment is to find out what factors affect the resistance of a wire in a circuit.

Prediction

I predict that a longer and thinner wire will have more resistance than a short and thick wire. This is because if the wire is longer, the current has a further distance to travel giving a higher resistance. Also if the wire is thicker, more electrons can pass through it at any time so the current passes it quicker.

Variables

Length of wire (will be varied)

Material of wire (will not be varied)

Thickness of wire (will not be varied)

Voltage (will not be varied)

Other factors

Apart from the variables above, there may be other factors that may affect the outcome of the experiment. These unlike the variables cannot be controlled, these include:

Impurities in the wire

Bad connections

Human faults (inaccurate readings)

Faulty components

We cannot control these variables so we will carry out the test 3 times and find the average.

Apparatus

Copper wire

Ammeter

Voltmeter

Power pack

Wires

Crocodile clips

The above apparatus will be used and set up as shown below:

Method

We will use the apparatus to set up the circuit as shown previously. The power will be set to 2 volts and kept that way throughput the test. The length of the copper wire will be changed from 5cm to 100cm; the figures shown of the Ammeter and Voltmeter will be recorded to enable us to work out the resistance of the wire using the formula

V/I=R Voltage/Current = Resistance

This test will be repeated twice giving a total number of 3 times. The results in the repeats will also be recorded and an average will be found out to ensure the most accurate results.

This is a preview of the whole essay

V/I=R Voltage/Current = Resistance

This test will be repeated twice giving a total number of 3 times. The results in the repeats will also be recorded and an average will be found out to ensure the most accurate results.

I will make my experiment a fair test by keeping the cross sectional area, the material of the wire and temperature of the wire the same. I will do this by using the same wire each time and making sure the wire doesn't heat up too much, but I have no control over the temperature so I'll just have to take it into account. The same components and layout of components will be used for each test and will not be changed.

Scientific Background

In a circuit, there are three things: the current, the voltage and the resistance. Current is the flow of electrons around a circuit and it cannot be used up, electrons flow from the negative terminal into the positive terminal. Current is measured in amperes and can be measured with an ammeter, which is connected in series in the circuit. The voltage is measured in volts the voltage is simply the driving force if the current around the circuit. Voltage can be measured by using a voltmeter, which is connected in parallel with the circuit. Resistance it simply the resisting power of a component in the circuit, from a lamp to a wire, everything has resistance. Different objects have a different amounts of resistance, for example a filament in a bulb has more resistance than a copper wire. Resistance is measured in ohms and can be measured by using the formula R=V/I . resistance can be very useful, it can protect fragile components in a circuit by the form of a resistor.

There are two types of circuits, series and parallel. In a series circuit, all of the components are put in a continuous line and the current is the same throughout the circuit. In a parallel circuit, the components are placed in many rows and are not continuous. The current splits in half at every junction and it joins together again at the end of the circuit. Voltmeters are placed in parallel to the circuit because the voltage is the same all around the circuit.

The relationship between current, voltage, and resistance is given by Ohm’s law. This law states that the amount of current passing through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor. This can be expressed as the formula which will be used in this test V=IR Voltage=Current x Resistance.

Results Table

Evaluation

As you can see from the results, the first set or results are quite different to the other two. This may have been caused by a bad or wrong connection in the circuit that has been fixed in the repeats. The first set of results will make a very different average than if only the repeats were calculated. I think that I could have improved this experiment by using better and more accurate equipment, a circuit that is set out better and repeated the test more times to get a more accurate results. Also, to get a wider range of results, I could have tested other factors of the wire for resistance like thickness of instance.

Conclusion

In conclusion, I think that I predicted correctly, as you can see in the results, the longer the wire, the higher resistance. I think that if I had tested for wire thickness as well, I think I would have come out with a thinner wire will have more resistance.