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The aim for this experiment is to find how a thermistor works and how temperature affects the resistance of current in the circuit.

Extracts from this document...

Introduction

Thermistors have many different uses, they can be used to protect the filaments of a projector lamp and T.V. tubes from current surges as they are switched on, they can also be used for fire and frost alarms.

Resistance shows how much current is flowing through, and how fast the current flow is. The greater the resistance, the more potential difference is needed to push a current through a wire. The resistance can be calculated by:

Resistance (R) =  Potential difference across the wire (V)

                   Current through the wire (I)

There can be many factors, which affects the resistance, some variables, which can affect my results, are:

Temperature- this can affect the resistance of the thermistor; it lowers the resistance and so allows more electrons to pass through.

Length and thickness of wire- increasing the length of wire will increase the resistance, as there will be a longer distance for the current to travel. The thicker the wire, the lower the resistance, this is because there would be more space for the electrons to pass through. To control this, will use the same wires each time I do the experiment.

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Middle

Apparatus:

-For this experiment, the equipment I need are:

-Ammeter – to calculate the current

-Voltmeter – to calculate the potential difference.

-Wire

-Battery/power pack

-Switch

-Thermistor

-Thermometer – this will be place in water with the thermistor.

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Conclusion

I will use the same length and thickness of wire; I can do this by using the same wires each time. Having different lengths and thickness of wire can speed up or slow down the speed at which the current flows. The longer the length the slower the speed, the thicker the wire the faster the speed of current.

I will start recording the ammeter and voltmeter after 10 seconds, because it may take time for the voltage to charge up.

I will wait between each repetition, for it to cool down.

And also I will take accurate readings, as this would ensure that I get reliable results. I should start reading when the ammeter and voltmeter are steady.  

The one variable I will change is temperature, which I am experimenting for, by doing this I can find out how temperature affects the resistance of the current in the circuit.

I must repeat the experiment five times, so that I can achieve a good set of results.

Safety points:

  • As I am not working with dangerous chemicals, safety glass is not required.
  • Don’t put the voltage too high.
  • Don’t touch wire while switch is on.
  • Turn power off while not doing the experiment.

OSMAN AHMADI        SCIENCE COURSEWORK        THERMISTORS

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