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# I am going to carry out an experiment to test what can be changed in a circuit to affect the resistance.

Extracts from this document...

Introduction

Introduction

We all know that current is the flow of electrons through an electrical circuit (the electrical charge), but before the electrons flow through the circuit, a voltage (or potential difference) must be applied. This provides the “pressure” to push the electrons forward. A battery for example would give a potential difference to a circuit and provide the force to begin the flow of electrons through it.

Resistance is measured in Ohms (Ω). It is anything in the circuit that opposes the flow of an electrical charge. Every component in a circuit causes a resistance (even the wire). The resistance in a circuit can be found by using this formula:

‘R’ is the resistance

‘V’ is the voltage

‘I’ is the current

For example, if the voltage in a circuit is 6volts and the current is 3amps then the resistance in that circuit would be 2Ω, as 6 / 3 = 2.

These variables are all relational. If you change one then it will affect the others. The formula to work out the voltage and current in a circuit are as follows:

I am going to carry out an experiment to test what can be changed in a circuit to affect the resistance. I will then record the results I get and analyse them to find out why and how it affects it.

Plan

Middle

0.57

0.04

0.45

0.8

0.13

0.74

0.08

0.54

6.75

0.07

0.45

0.04

0.42

0.7

0.15

0.76

0.09

0.57

6.33

0.08

0.53

0.04

0.41

0.6

0.11

0.72

0.07

0.51

6.97

0.06

0.47

0.05

0.35

0.5

0.13

0.73

0.09

0.50

5.37

0.08

0.44

0.05

0.32

0.4

0.18

0.70

0.11

0.45

4.09

0.09

0.39

0.06

0.26

0.3

0.23

0.66

0.15

0.40

2.67

0.16

0.32

0.06

0.21

0.2

0.27

0.67

0.17

0.41

2.37

0.18

0.32

0.09

0.23

0.1

0.30

0.65

0.19

0.39

2.02

0.20

0.30

0.08

0.21

Results

Nichrome 32SWG

 Length of wire (m) Current (A) Voltage (V) Average current (A)

Conclusion

Conclusion

I am very confident that these results are trustworthy. Indeed it does show on the 28 and 32 SWG graphs that there are some anomalous results, but there is still a clear pattern that:

The thicker the wire is the less resistance is in the circuit. This is because the electrons and particles have more space in the circuit to move. If the wire was thinner then the particles would have less room and this would cause more collisions with other particles, thus the resistance will be higher.

The longer the wire is the more resistance is in the circuit. This is because there are more particles for the electrons to collide with if the wire is longer and so this will increase the resistance.

Evaluation

If I had performed this test again I would definitely strive for more accuracy with my results. Although a clear pattern still emerged from them I feel that they were not up to my standard.

On this experiment I was manually setting the rheostat’s power by hand, so this was bound to create some minor errors. If I could get hold of some equipment that would let me input values into a rheostat to make sure that it is set to the same power every time, then I would definitely use it, as it is likely then that the accuracy of my results would improve.

Jack Whitehead – 11AG        Physics Coursework

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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