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# Investigation in to what happens to the resistance of a thermistor as its temperature changes.

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Introduction

Physics Coursework

Danielle Roots

Mr Small

Aim:  To investigate what happens to the resistance of a thermistor as its temperature changes.

What is a thermistor?

Is a resistor that changes in resistance with temperature.

“Its principle characteristic is that their electrical resistance changes in response to changes in their temperature.”

http://www.betatherm.com/therm_theory.html

Symbol for a Thermistor:    Calculating resistance

Resistance in a circuit can be calculated using the levels of voltage and current in a wire or a single component.

The formula we use to measure resistance is:

RESISTANCE = VOLTAGE                        R = V

CURRENT                          I

What is Current?

Current is the flow of electrons around an electric circuit.

It is measured in amps.  Current is measured in Amps.

1 amp = 1 coulomb per second

Per means divided by so current = charge

time          Middle                         [                    Parallel Circuits Series Circuits

Only has one path for the charges to move along. Charges must move in "series" first going to one resistor then the next. If one of the items in the circuit is broken then no charge will move through the circuit because there is only one path. There is no alternative route. In a series circuit voltage decreases as it travels around the circuit as the energy is being used up.  The current however will stay the same wherever it is measure around the circuit.

The voltage used on each component add together to equal the reading from the voltage source.  Linking this to the equation   V = R

I

And the higher the voltage is going to be because the higher the resistance is because the current stays the same.

Ohms Law

Ohms law clearly states that

Resistance =  Voltage

Current

Conclusion

The same thermometer or at least the same type of thermometer I will use a liquid thermometer all the time because the readings I get could be different because of a thermometer being too or not accurate enough compared to other thermometers I used previously but in the same investigation.When I repeat results if I have time I want to wait until the thermistor cools down so this doesn’t affect the results because the heat of the thermistor could be different from that of the water and the results I get aren’t correct because the current and voltage results I am taking aren’t in relation to the temperature of the water because doing this experiment I am assuming he thermistor is the same temperature as the water.

Safety

• I have to make sure none of the wires are in the water or are on something hot in case they burn etc.
• When taking apparatus apart I need to make sure that I am careful I don’t burn myself
• That I wear goggles in case of any fires or water boiling and bubbling into eyes.
• That I don’t fill the water up too high on the beaker in case it splashes out and burns someone

Prediction

Scientific Theory

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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