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Investigate how resistance can affect the amount of current flow.

Extracts from this document...

Introduction

Physics coursework.

Resistance investigation.

Introduction.

In my experiment I will investigate how resistance can affect the amount of current flow. Vibration or movement of the metal atoms causes the resistance. This means that all metals will have resistance because they all contain atoms, which vibrate.

Key factors.

The flow of electrons along a conductor (e.g. a wire) is called a current. The size of the current flowing will depend on a number of variables. Any wire will resist the flow of electron, this is affected by:

  • Length of the wire
  • Thickness of the wire
  • Material which the wire is made of
  • Temperature of the wire

Resistance

The resistance of an object is determined by the nature of the substance of which it is composed, known as the resistivity, the dimensions of the object, and the temperature. Resistivity is expressed in terms of the ohms resistance per cubic centimeter of the substance at 20° C (68° F).

The term resistance is also used when the flow of a fluid or heat is impeded. The forces of friction provide the resistance to the flow of a fluid in a pipe, and insulation provides thermal resistance that reduces the flow of heat from a higher to a lower temperature.

Property of any object or substance to resist or oppose the flow of an electrical current.

...read more.

Middle

10 cm

6.50 A

0.5 V

0.08 Ω

20 cm

5.09 A

0.5 V

0.10 Ω

30 cm

3.59 A

0.5 V

0.13 Ω

Length of nichrome (thickness 32)

Length of wire

Current

Voltage

Resistance (Ω) = Voltage / Current

10 cm

0.26 A

0.5 V

1.92Ω

20 cm

0.13 A

0.5 V

3.84Ω

30 cm

0.08 A

0.5 V

6.25Ω

From my preliminary results I can see that copper is good conductor of electricity and huge amount of current are passing through. Also resistance was extremely low, because a lot of current was passing. On the other hand nichrome is bad conductor of electricity and current is really small. Therefore resistance is high. In my real experiment I decided to use nichrome instead of copper because I want to keep current low and have high resistance to make the graph look better.

Aim.

In this experiment, I want to examine the effects of different lengths of the wire on the current, to examine how much the resistance is changed when we increase or decrease the length.

Method.

I started my experiment by building the circuit:

I had to cut the nichrome wires different length from 10 cm to 80 cm. I took current readings from the ammeter. I used constant voltage 1 V in the first result table and 2 V in the second result table. During the experiment I measured current twice for each length of wire. That was necessary to get the most accurate results.

Safety.

In my experiment some safety precaution were needed.

...read more.

Conclusion

Our data is accurate and supports our conclusion, for instance, the duplicate results (for test1 and test2) are very close.

The method of course, was an amateur one. There can me many improvements. We could get more trusted results if we had used a better wire that would not get hot fast or become burned; such a wire won't affect our fair test because of it's getting hot or etc due to it's low quality. The noting of the current would be much more accurate if there would be some kind of memory in the ammeter, to save the results itself without us needing to keep an eye on it every time which causes small mistakes, data logging equipment in this case can be very useful.

Considering that we only had the very basic equipment to carry out this experiment, it was not bad. However it could have been better if I would have used a more accurate way to measure the length of the wire and a constant account of the temperature of the wire would help as well. This would help me to see when the temperature of the wire is back to normal again.

For this purpose I should have used a computer which detects the temperature of the wire and if the wire would get hot computer would show it.

References from: Encarta Reference Library 2002  

...read more.

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