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# What is resistance?

Extracts from this document...

Introduction

GCSE Physics Coursework

Theory

What is resistance?

Electricity is conducted through a conductor. The number of free electrons depends on the wire and more free electrons means a better conductor. The free electrons give lots of energy and then they collide with other free electrons. This happens across the wire and then electricity is conducted. Resistance is the result of energy loss as heat. The collisions turn the energy into heat.

How is it measured?

Resistance of a length of a wire is measured by the current and the voltage across a wire.

Formulas -

I   =

R  =

V =  I x R

Factors affecting Resistance

• Length of a wire can affect the resistance of a wire because there are more atoms in a longer wire for the electrons to pass through.
• Material of a wire can affect the resistance of a wire because some materials resist the flow of electrons more than others.
• Thickness of a wire can affect the resistance of a wire because there is more room for electrons to pass through so the thicker the wire the less resistance.

Ohm’s Law

The size of the electric current flowing through a conductor depends on the voltage across it, and the resistance of the conductor. When the voltage is increased, the current increases. The current is the same as the voltage if the temperature remains the same. The German physicist Georg Ohm formulated this in the 1920’s. If the voltage is doubled, the current will also be doubled.

Planning

Aim

I am going to investigate the resistance in a wire of the thickness of 34swg of different lengths. I will do this investigation 3 times to get it accurate.

## What I will keep the same

• Thickness of wire.
• Temperature of wire.
• Material of wire.

Middle

40

2.55

0.25

10.20

30

2.31

0.31

7.45

20

1.94

0.40

4.85

10

1.32

0.55

2.40

## Length (cm)

Voltage (Volts)

Current (Amps)

Resistance (Ohms)

100

3.08

0.11

28

90

3.02

0.13

23.23

80

2.97

0.14

21.21

70

2.88

0.15

19.20

60

2.82

0.18

15.67

50

2.72

0.21

12.95

40

2.51

0.24

10.46

30

2.30

0.28

2.71

20

1.92

0.34

5.65

10

1.29

0.55

2.35

## Length (cm)

Voltage (Volts)

Conclusion

My results also showed that when the length was doubled the resistance also was doubled, my prediction was correct. The prediction told us that if I doubled the length, the resistance would also double, I know this as this my theory tells me that electrons collide with other free electrons across the wire, this making energy and if the length was doubled there would be more collisions meaning more resistance and that’s what exactly happened.

## Evaluation

My investigation was accurate as the 3 sets of results and graphs all looked about the same. My prediction was also correct has when I did the experiment it done what I predicted. I could improve the investigation by using an ohmmeter to measure the resistance (to get a more accurate result).

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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