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Discover how the voltage is affected when the current flows through wires of varying lengths.

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Introduction

Helalur Rahman Khan 3894 10.1

Ohms Law

My aim is to discover how the voltage is affected when the current flows through wires of varying lengths.

Scientific Introduction

In 1826, a German physicist George Ohm stated ‘the current in a conductor is proportional to the potential difference between its ends’, providing physical conditions like temperature stay constant. The word ‘proportional’ means that when you double the potential difference the current is also doubled automatically.

Resistance is anything in the circuit that slows the flow of electrons round the circuit. This means that if you increase the resistance then the less current will flow or more voltage will be needed to keep the same current flowing. To calculate resistance you can work it out by using the formula R=V/I. This means that resistance= voltage/ current. Resistance can be affected by temperature; if the temperature is constant then the current will be proportional to the potential difference.

Using this formula for ohms law is very important as it can find you the potential difference, current or resistance using what the circuit has. The formula is:

V (Potential Difference)=I (Current) x R (Resistance)

V=IxR

Resistance is measured using resistors, all resistors produce heat when a current flows through it. The unit resistance is measured in ohms (Ω).

An electric current is the rate of flow of charge through a surface. Current is represented by the symbol I, and its unit is the ampere (A). The current is the flow of electrons through a circuit.

...read more.

Middle

0.93

0.93

0.77

0.93

0.83

30cm

1.08

1.08

1.10

0.87

0.86

0.87

1.09

0.87

1.25

40cm

1.36

1.37

1.37

0.83

0.82

0.83

1.37

0.83

1.65

50cm

1.60

1.61

1.62

0.76

0.77

0.77

1.61

0.77

2.10

60cm

1.80

1.84

1.83

0.71

0.71

0.72

1.82

0.71

2.56

70cm

2.00

2.01

2.01

0.67

0.66

0.67

2.01

0.67

3.01

80cm

2.17

2.16

2.18

0.64

0.64

0.64

2.17

0.64

3.39

90cm

2.33

2.33

2.32

0.61

0.61

0.61

2.33

0.61

3.81

100cm

2.49

2.50

2.48

0.58

0.59

0.59

2.49

0.59

4.24

Preliminary investigation at 4.5V & 5.95A

10cm- 3A & 1.40V

100cm- 0.75A & 3.24V

Length of wire

Volt reading in Volts (V)

Amp reading in Amps (I)

Average reading

Resistance in Ω

...read more.

Conclusion

The procedure of the experiment was very good as it was very safe for my partners and myself. The wire was placed on a metre ruler so that you could measure the length of the wire easily. The experiment could have been improved by using digital ammeters so that you can get an accurate reading, the analogue ammeter could only read up to 1A, which meant that the ammeter couldn’t be used on an experiment checking the amp reading over 1A. Other than this I think that the experiment procedure was very good.

During the experiment I took down three readings for the voltage and amps from 10cm to 100cm. This made the evidence reliable because an average could be worked out from the readings. A problem with this was that the ammeter and the voltmeter was never still, it always changed from the first reading on the screen. The evidence was sufficient enough to support the conclusion, which proved my prediction right.

To make my work I could have added two ammeters on the circuit so that I could have got a more accurate reading, I could have also done the experiment on a longer wire I could have gone up to 300cm to see how the resistance is compared to the 100cm. This would have been a good experiment as light switches are sometimes a metre away from the light. Other then that the experiment was a good way to find out about resistance along a wire.

Bibliography

Physics a course for GCSE: Gilbert Rowell and Sidney Herbert

Modular Science for AQA: Keith Hirst, Mike Hiscook, David Sang and Martin Stirrup

NEAB Modular science: Richard Parsons

...read more.

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