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Factors affecting the resistance of a metal wire.

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Introduction

Physics Investigation

Factors affecting the resistance of a metal wire

Planning

        I have been asked to consider the factors affecting the resistance of a metal wire. Resistance opposes the flow of an electric current around a circuit. So that energy is required to push the charged particles around the circuit. Resistance would occur when the electrons travelling along the wire collide with the atoms of the wire, causing the flow of electrons to slow.

 I will find out the resistance, using the equation:

Resistance (Ω) = Voltage (V)

                             Current (A)    

...read more.

Middle

Trial Results

Material

Thickness

(mm)

Length

(cm)

Current

(A)

Voltage

(V)

Resistance

(Ω)

Nichrome

0.274

100

0.050

0.19

3.8

0.274

100

0.100

*

0.274

100

0.150

*

0.457

100

0.050

0.35

7.0

0.457

100

0.100

0.71

7.1

0.457

100

0.150

1.07

7.13

* The highest ammeter reading that I could get was 0.083A even with three cells. This reading was not high enough to obtain the readings for 100mA and 150mA. The wire was the thin wire; therefore I can change to the thick wire. This should have less resistance, thus obtaining higher ammeter reading. This should have less resistance because the electrons have more space to move freely.

Experiment Plan

Prediction: I predict that as the length increases, the resistance will increase. The electrons would collide with the atoms of the wire. If the length of the wire were to be doubled or tripled, the resistance would also be doubled or tripled.

Range of measurements: I will choose the 200mA range. In previous homework, I have seen how sensitive different ranges can be. In the 10mA range, the sensitivity is every 0.01A. I feel that this is not sensitive as the 200mA range, which produces a hundred times sensitivity, 0.0001A.I have chosen the range of 50mA, 100mA

Equipment:

  • Three cells (each 1.5V)
  • An ammeter on 200mA range
  • A voltmeter on 20V range
  • A potential divider (16Ω)
  • Nichrome wire - thickness 0.457mm - length 300cm
  • Crocodile clips
  • Connecting wires (2 long wires)
  • Metre rule
...read more.

Conclusion

I have no anomalies to account for into reasoning why the result was obtained.

To change the variable in order to extend the range of evidence, I would perhaps have chosen a longer length of wire to test on. This would have been perhaps 400cm, just to acquire more results of a 25cm gap. I believe there would be sufficient and enough evidence for the conclusion.

To repeat with a different material would be such as copper would be motivating. Copper is used for connecting wires, as it is a good conductor. Thus, the copper would heat as the current is flowing through it, and temperature is one of the four factors that affect resistance. However Nichrome is used in the heating elements of electric fires. To see whether Copper or Nichrome would be suitable, I would set up a series circuit with a 30cm part of both wires with an ammeter and voltmeter with 3 cells. Using only my touch senses I would see which would heat more than the other, as I know that voltage is shared between the components, and it would be a fair test.

...read more.

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