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# Which Factors affects the resistance of a wire?

Extracts from this document...

Introduction

Which Factors affects the resistance of a wire?

Current is a flow of electrons and the resistance is when the electrons are pushed through the conductor they collide with the atom of the copper wire making them vibrate more vigorously.

The more resistance a resistor has, the more volts are needed to push each ampere through. If the voltage across a resistor and the current through it have been both measured, the resistance can be calculated using the equation:

Resistance = Voltage

Current

Or

R = V

I

Where V is voltage (Volts) and I is current (Amps). This is Ohm’s law.

There are four factors that effect resistance:
1)
Temperature When the temperature of a metal increases the resistance of that metal increases. This is because when the temperature increases the atoms of the metal vibrate more vigoursly because of the increase in energy. This means that the electrons have more difficulty getting through the wire as they collide with the atoms, which are in their pathway.  This increases the amount of collisions therefore there is more resistance. However it is hard to keep the temperature exactly the same as the room temperature might change from day to day. It is essential to use a low voltage because it means a low current that will not heat up the wires. If a high voltage is used the energy would be in form of heat which would make the experiment unfair. The investigation will be done at room temperature.

Middle

30 swg

0.5

1.1

1.1

0.122

Average resistance:

 Thickness (swg) Resistance (ohms) 22 swg 1.07 26 swg 1.03 30 swg 2.35

My second results are for different materials at a fixed length with the same thickness.

Different materials

 Metal Current (amps) Voltage (volts) Resistance (ohms) Diameter (mm) Nichrome 0.53 1 1.89 0.546 Copper 2 1.3 0.15 0.545 Constantan 1.2 0.7 0.583 0.54

 Metal Current (amps) Voltage (volts) Resistance (ohms) Diameter (mm) Nichrome 0.7 1 1.43 0.546 Copper 2 1.3 0.15 0.545 Constantan 1.45 0.6 0.41 0.54

Average resistance:

 Metal Resistance (ohms) Nichrome 1.66 Copper 0.15 Average resistance 0.49

My third results are for the material copper at a fixed length with varying thickness.

#### Copper

 Thickness (swg) Current (amps) Voltage (volts) Resistance (ohms) Diameter (mm) 20 swg 2 0.2 0.1 0.55 26 swg 2 0.2 0.1 0.54 32 swg 1.89 0.4 0.2 0.28

 Thickness (swg) Current (amps) Voltage (volts) Resistance (ohms) Diameter (mm) 20 swg 2 0.2 1.04 0.55 26 swg 2 0.2 0.74 0.54 32 swg 1.85 0.5 1.8 0.28

Average resistance:

 Thickness (swg) Resistance (ohms) 20 swg 0.1 26 swg 0.1 32 swg 0.24

Conclusion

• Some of the tables showed anomalies, which could have been minimised, with many more repeats and a greater range giving more reliable data.
• More accurate measuring devices i.e. voltmeters and amp meters which would produce more accurate figures.
• If the test were carried put in a temperature-controlled environment less anomalies would be seen.
• We could have tried more materials to give a wider scope.
• Instead of connecting the voltmeter to the main circuit I would connect it to the wire, which is being tested. I would do this so that the voltmeter is measuring the voltage of just the wire being tested and not the wires of the main circuit as well
• I would use a digital voltmeter instead of an analogue meter. I would do this because a digital voltmeter is a lot more accurate than an analogue because if the needle in the analogue voltmeter is bent then the readings given off will be false whereas a digital voltmeter does not rely on a needle or any other manual movements.
• I could have done the test for the temperature of the wire but I would not have been able to carry out a fair test because it is extremely
difficult to produce and control the range of temperatures needed without the correct equipment.
• To make the experiments more reliable all apparatus should have been checked to see if it is functioning properly and is giving a true reading. This would then partly avoid systematic error.

Overall the predictions I made were proved to be correct. So proving the factors that affect the resistance of a wire is:

1. Material
2. Length
3. Temperature
4. Cross section area

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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