# To investigate how the resistance of a wire changes.

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Introduction

Physics coursework yr10: Resistance of a wire

Planning

Aim: To investigate how the resistance of a wire changes

Key factors:

- Voltage across wire (higher the voltage, the faster electrons flow and the resistance does not change)
- Current in circuit (higher the current the more electrons going through the wire, so more resistance)
- Length of a wire (the longer the wire the more resistance)
- Thickness of wire (the more thicker the wire the less the resistance there is)
- Light dependant resistor (light intensity decreases the resistance increases)
- Temperature (If temperature gets too high then wire could melt and if temperature gets too low then wire could snap).

Prediction:

I predict that the longer the wire, the higher the resistance. This is because if the wire is short the electrons will flow straight through and not bump/collide into each other, but if you increase the wire length the electrons have to travel further and this means that they will collide more into each other, creating more resistance. Also the more current there is, the more resistance there is, because the more electrons there are in the wire the more they will collide into each other. If you increase voltage the electrons flow faster and not collide as much.

Middle

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Observations

Did I make some measurements?

Yes I made measurements of current, voltage and length of wire.

Are my measurements appropriate?

Yes my measurements are appropriate because we are testing how the resistance of a wire changes depending on the length, this indicates that length is an appropriate measurement. We need voltage and current to work out resistance. I put length in cm, volts in V(volts) and current in A (amps).

How will I record my observations?

I will record my observations on a table and plot the average results of resistance on a table.

Did I measure correctly?

I measured correctly because I used an ammeter to measure current, a voltmeter to measure voltage. I used these so I could take down the readings and calculate the resistance.

Did I take enough measurements?

I took enough measurements because I can work out resistance, with the two measurements of current and voltage. I also took measurements of length so I could compare whether or not, when the length increases the resistance decreases.

Will I repeat my measurements?

Yes, I will repeat my measurements three times.

Is my range correct?

My range is correct because I took readings every 10cm and that is what I am supposed to do & also there is an equal amount of difference between each length. E.g. 10 20 30 etc.

10 10

Did I use my apparatus with skill so that the readings will be accurate?

I used my apparatus with skill by putting the voltmeter in parallel with the circuit (produce too much resistance in series). And by putting the ammeter in series with the circuit.

Do my results contain the correct number of digits?

My results contain the correct number of digits because they are to 2 d.p.

Results:

Observation results one:

Length (cm) | Voltage (V) | Current (A) | Resistance (Ω) |

100 | 1.35 | 0.49 | 2.75 |

90 | 1.33 | 0.53 | 2.50 |

80 | 1.32 | 0.61 | 2.16 |

70 | 1.29 | 0.71 | 1.81 |

60 | 1.13 | 0.93 | 1.21 |

50 | 1.07 | 0.95 | 1.12 |

40 | 0.98 | 1.15 | 0.85 |

30 | 0.83 | 1.18 | 0.70 |

20 | 0.49 | 1.66 | 0.29 |

10 | 0.03 | 2.47 | 0.01 |

Conclusion

Yes. The results followed the theory that resistance is directly proportional to length.

Can any additional work be done?

I can make more graphs. I could make a graph for each observations set of results. After making the graphs I could compare the three graphs and see if they look fairly the same. If they do I will know that the experiment gave out fairly the same type of results each time and that each experiment was tested fairly and correctly each time. We could test the same type of wire but thicker in diameter. It would be the same test conditions but the only part I will be changing is the thickness of the wire. I would test the thicker wire three times and get three sets of results again and make graphs for each set of results. I would compare the tables and graphs of the thicker and thinner wires. I would test this to see if you increase the thickness of the thinner wire then will the resistance increase or decrease for each type of length e.g. thin wire (20cm): 0.50 volts, thick wire (20 cm): ?. The thick wire resistance might be double that of the thin wire. If it is double, I could then work out how much resistance there is for a wire 10 times as thick as the thin wire and create an equation for it as well.

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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