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# Current flowing in a wire

Extracts from this document...

Introduction

Planning

Title

An investigation into the current flowing in a wire.

Method

1. The apparatus was set up as shown in the diagram below.
2. Three readings were taken at each length on each wire; the same voltage had to be used through (2volts).
3. The results on voltage and current were recorded and an average was taken.

The wire resistance was calculated from the average figures.

Diagram

Related knowledge

In this experiment I am making an investigation into the current flowing in a wire. I will explain how I will attempt to do this.

Firstly I need to discover what resistance is; resistance is an opposition offered by a circuit to the passage of a current through it. Resistance is calculated using ohms law [resistance = potential difference (in volts) / current (in Amps)]. There are four factors affecting resistance:-

1. temperature
2. length of wire
3. cross sectional area (thickness)
4. material of the wire

1. Temperature: If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are increasingly moving into the path of the electrons. This increase in collisions means there will be an increase in resistance.

2.

Middle

Therefore i have confirmed that my prediction was correct and that as the length of the wire increases, the current will decrease and the voltage will increase. I think this is because as the length of the wire increases, the resistance increases, therefore the current will be less due to more resistance. Electrons are pushed out through the wire at the beginning of the circuit. This electrical pressure is measured in volts (V). Across the whole circuit, each resistor i.e. light bulbs, buzzers etc. (anything which tries to restrict the electrons movements)  there is an electrical pressure difference which occurs, called potential difference or voltage, measured in volts (V) this data can be collected with a voltmeter. The voltage needs to be measured at two places within a circuit due to the pressure difference which is lost in the circuit. One end will be measuring where the circuit starts on the wire and the other where it finishes on the wire. Consequently the voltage will increase, because as the resistance in the circuit increases there will be a bigger pressure difference along the wire. Therefore the voltage reading will be higher because the potential difference will increase.

Conclusion

Crocodile clips, to connect the wire to the circuit.Three copper wires (one thick, one medium and one thin).A digital ammeter, to measure the current accurately. A digital voltmeter, to measure the voltage accurately.A ruler, to measure the length of the wire to be used.

Method

• Set up the equipment as shown in the diagram of the circuit, picking one of the three wires to start with and a length (e.g. 10 cm). Make sure the power pack to two volts.
• Turn the power pack on so that you have just enough time to take a reading from the digital ammeter and voltmeter and turn it off. This will prevent the wire getting hot and skewing the next set of results. You are looking to read the voltage and current to two decimal places.
• Next, move a crocodile clip up ten centimetres and repeat the above process.
• Once done, keep moving the clip up in steps of ten centimetres at a time up to 90cm, repeating the aforementioned process each time.
• Run the entire step process for each length on all three wires twice (i.e. Two runs for each wire).

The results for this experiment should show a contrast in results from copper wiring to nichrome wiring, as nichrome offers more resistance than copper.

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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