Potential difference or voltage- increasing the potential difference will increase the power of the current, so the electrons will move faster through the circuit. Potential difference is measured in voltage using a voltmeter. To control this I will keep it constant by using a voltmeter and make it has the same reading each time.
To find the rate at which the resistance of the thermistor decreases, I will find the gradient for my results. The gradient will show how fast or slow the rate of resistance falls. I will use the gradient formula:
Gradient = Y1 – Y2
X1 – X2
Aim:
The aim for this experiment is to find how a thermistor works and how temperature affects the resistance of current in the circuit. I will do this by first carrying out a preliminary test; this would help to find out at which condition the experiment works best.
Prediction:
I predict that a thermistor wills increase the resistance in a circuit. Using a thermistor in a circuit will only allow a few electrons to pass through but as the temperature rises the resistance will lower and allow more electrons through.
From my research I have found that with a thermistor, the current is resisted and not able to flow through when it is cold. However, as the temperature increases the resistance decreases and so electrons can flow at a faster rate.
Before doing this experiment, I will carry out a preliminary test to find out the best possible condition for my experiment to work and enable me to achieve a reliable set of results.
Preliminary test:
Aim:
To find out the best way of getting the most accurate results for this experiment and also find out which condition the experiment works most efficiently.
Results:
I think that the preliminary test ran quite smoothly, and as expected.
I will next time concentrate on reading the ammeter and voltmeter more accurately. I also got an appropriate set of results.
Conclusion:
The results prove that as the temperature rises the resistance reduces.
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.
I will set out the equipment like this:
Method:
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The range of temperature I will use is 10, 15, 20, 25, 30, 35, 40, 45 and 50 (all in oC). So it will rise by 5oC each time I record.
- Make sure the battery/power pack is turned on. And check that the voltmeter and ammeter are reading correctly.
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Measure the temperature, to make sure it is below the starting point 10oC.
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Start heating, and as the temperature rises up 5oC each time I must record the ammeter.
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When the temperature reaches the finish point 50oC, I will stop and turn off the battery/power pack. And wait until temperature falls below 10oC.
- I will repeat this process 5 times so I don’t get any bias or unreliable results.
Fair test:
To make this a fair test, I must keep the variables-potential difference constant, use the same length of wire, start recording the ammeter and voltmeter after 10 seconds, wait between readings, take accurate readings.
To keep the potential difference constant I will use the same powered battery or I can use a power pack and set it at the same point each time. I will keep this constant because, as the potential difference increases, it also increases the power of the current, so the electrons will move faster through the circuit, and so it will give me an unreliable result.
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.