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

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.”

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

What is resistance?

Resistance is the measure of how much the current is slowed down.  The bigger the resistance, the smaller the current.

Resistance is measured in Ohms (symbol Ω).

What Causes Resistance?

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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

Which would mean as the current increases in a circuit so would the voltage because the resistance stays the same and for example if there is higher voltage if the current doesn’t increase then the calculation for resistance would be higher so the current has to increase at the same time.   A graph comparing voltage against current should look something like this:

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