# An investigation into Resistance

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Introduction

## An investigation into Resistance

GCSE Physics Coursework

An investigation into Resistance

Daisy Roberts

Plan:

Electrical resistors or resistance can be made in many different ways. One way is to wind wire into a coil. The task is to investigate what factors control or change the resistance of wires.

Background information:

Resistance: Opposes the flow of current and is defined as potential difference over current, and is caused by particles getting in the way of moving electrons, slowing down current flow in a material. The unit of resistance is the ohm (Ω). This equation can be formulated by R=V/I with I= current in amperes, V= potential difference in volts and R= resistance in ohms.

Resistivity: Resistance can also be worked out using the following equation:

Resistance = resistivity x length /area of cross section

Or = constant x length /area of cross section

The constant depends on the type of material and is referred to as the resistivity of the material. The unit of resistivity is the ohm metre (Ω m). If the resistivity of a material is known, the resistance of a given length of material of known area of cross-section can be calculated.

A resistor: Is a component designed to have a specific resistance. Accurate resistors can be made from metal wires.

Middle

2.5

1.4

1.786

10

2.5

2.4

1.042

Conclusion: From this experiment, I have seen that the range I have used is good and will produce a good graph. However, there were a few problems. I used an analogue ammeter, which meant there were inaccuracies when reading off the level of volts and amps. I also found it was time consuming to work out the resistance for each result, so I have decided to use a mutli-meter for my experiment which would also give much more accurate results. I will also need to do repeats of the readings to gain a fair average.

Circuit diagram:

Apparatus list:

Multi-meter

Connecting wires

Crocodile clips

Length of wire required

Ruler

Detailed plan:

Set up the circuit above

Begin with 100cm of wire, place in the circuit between the crocodile clips and measure the resistance using the mutli-meter and record results.

Conduct this for values of 10cm intervals down to 10cm.

Repeat each value 3 times to gain an average

To keep the other variables the same, make sure the experiment is kept constant at room temperature, the same wire is used throughout (Nickrome (125g) 26 SWG), and that the same width of wire is used (diameter 0.457).

Risk assessment:

To sustain safety, it is important to consider that there is electricity in use.

Conclusion

Anomalous results: I did not have any anomalous results to my data apart from the few discrepancies that may have occurred with the measuring of the wire.

Changes: there are few changes that could be made to improve the results produced from this experiment as the results are pretty accurate already, but a larger range of results could be an improvement, and also more attempts at the same value could produce a fairer average. Measuring the wire for every 5cm could also make readings more accurate.

Is the evidence enough to support a conclusion? This evidence is enough to support a conclusion about the affect the length of wire has on resistance, but not about the affects that all factors affecting resistance have.

Further investigations: obvious investigations that could be carried out after this would be to look into and test how the other factors affect resistance in a circuit. This would then provide enough evidence to support a conclusion on resistance.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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