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Factors Affecting The Resistance (Thickness)

Extracts from this document...

Introduction

Investigating the factors affecting the resistance

Name: Sukhdev Singh Shah

Form: 10GK

Introduction:

Resistance:

Electrons move more easily through some conductors when a potential difference is applied. Resistance is determined by how good or bad a conductor a material is.

A good conductor has a low resistance while a poor conductor has a high resistance.

OHM Ω

Resistance is defined by: R= V/I

If I= 2A when V= 12v, then R= 12/2 = 6 Ω

Resistors:

Some conductors are made from carbon or alloy wires, and are intended to have resistance, so we call them resistors. Resistors used in everyday life have values ranging form usually a few ohms, but go up to millions of ohms.

Resistors in a series:

The resistors below are in Series. The current flowing through all (I) is the same, and the separate potential difference across then is the same as the total potential difference across the 3 (V).

i.e. V= V1 + V2 + V3

If R is the combined resistance, V= IR

Resistors in parallel:

The resistors below are parallel. The total current (I) equals the sum of the currents in the separate branches, and the potential difference between the ends of each is the same.

i.e.

Middle

A.C Power Pack                                                        Variable Resistor

Circuit Diagram:

Method:

• I will set up the circuit as shown above.
• I will connect in a series circuit with an A.C. power supply, setting the value to an appropriate voltage.
• I will then connect a wire which has a thickness of 26cm to the output from the ammeter.
• I will then connect the voltmeter across the wire I am testing.
• I will then connect the negative terminal of the voltmeter to the negative terminal of the power supply, therefore completing the circuit.
• I will repeat the above process for all the required thicknesses of wires that are going to be experimented.
• Because the thinner wires become quite hot, the readings must be taken quickly, but I will allow the wire to cool down before the next reading.
• I will repeat the whole experiment again, this time starting off at the thickest wire and going down to the thinnest.
• I will then record the resistance for each thickness of wire after the wire had been disconnected from the circuit.

Prediction:

I think as you increase the thickness of the wire, you also increase the amount of resistance.

Conclusion

The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material, so if there is a larger number of atoms there will be a larger number of collisions which will increase the resistance of the wire. If a certain thickness of wire contains a certain number of atoms when that thickness is increased the number of atoms will also increase.

Evaluation:

I enjoyed carrying out this investigation. I didn’t come across any problems while trying to set up the circuit. Everything was done correct and I got no anomalous results when I took the readings. These results aren’t very accurate because I only took one reading for each length of wire. If I had taken two or three readings for each length, then I could have found the average. This would have been more accurate. If I did this experiment again then I would use a resistor rather than a variable resistor because the results are unreliable. They are unreliable because everyone would have different results due to how they set up the resistance on the variable resistor.

Sukhdev Singh Shah 10GK                28/04/03

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