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How the Length of a Piece of Wire Can Affect the Resistance Within the Circuit.

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Introduction

Physics Coursework

Problem

I am trying to find out how the length of a piece of wire can affect the resistance within the circuit.

Background

Resistance

With an energy source, such as a battery or a generator, the size of the current that flows is decided by the resistance of the circuit. The bigger the resistance within the circuit, the harder it becomes for electricity to flow through the circuit. The resistance within a circuit is measured in Ohms (Ω).

Structure of Metals

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When a potential difference is applied, the electrons gain energy and this causes them to move in the same direction as the current. As electrons pass along, the metal, there will be collisions with the metal ions this causes the metal to heat up this is due to energy transfer in the collision. The electron flow of the current reduces when this happens.

...read more.

Middle

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Circuit

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                                                                                    Sliding contact
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Apparatus

This circuit diagram displays: 3 Batteries, 1 Rheostat (Variable Resistor), 1 piece of 100cm Nichrome wire, 1 Ammeter and 1 Voltmeter. The Voltmeter is connected across the Nichrome wire because it is measuring the potential difference between it’s ends; the + terminal is connected to the + side of the circuit.

Method
  • Connect the circuit as shown in the diagram above.
  • Adjust Rheostat to different values i.e. 0.3A, 0.5A etc Do these readings for multiple wire lengths.
  • Record readings at the voltmeter, which records the voltage, and the ammeter, which records the current. These records will be stored in a table.
  • Draw a graph of results displaying the readings on the ammeter and the voltmeter.
Variables

Independent Variables: This is what I will change during the experiment, such as the length of wire.

Dependant Variables: This is what will change due to the “Independent Variables” such as the Resistance.

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Conclusion

W (V)

W (A)

W (Ω)

10

X (V)

X (A)

X (Ω)

20

Y (V)

Y (A)

Y (Ω)

30

Z (V)

Z (A)

Z (Ω)

40

This is a small example of what the table will be like. In the experiment I would continue to go up sequentially in tens until the length of wire reaches 90cm. I will then take another reading from where the length of wire remains the same but the rheostat will have been changed. The current throughout the experiment will remain the same. For safety reasons and to make this a fair test we have to let the Nichrome wire cool down before we test another length for resistance.

After I have completed two tables like the one shown above I will create a table with the average of the two resistances.

Resistance (table a)

Resistance (table b)

Average Resistance (Ω)

Wire Length (cm)

W (Ω)

W (Ω)

W (Ω)

10

X (Ω)

X (Ω)

X (Ω)

20

Y (Ω)

Y (Ω)

Y (Ω)

30

Z (Ω)

Z (Ω)

Z (Ω)

40

The information from the table will be put onto a graph:

Predicted Outcome

Average Resistance (Ω) in Ohms

                                                          Wire length (cm) in centimetres

...read more.

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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