• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The aim of my investigation is to see whether the resistance of a thermistor (a type of temperature sensitive resistor) is directly proportional to the temperature.

Extracts from this document...

Introduction

Carl Payne        Physics Coursework

The aim of my investigation is to see whether the resistance of a thermistor (a type of temperature sensitive resistor) is directly proportional to the temperature. Also I aim to see whether the length of the wires in the circuit affects the resistance. I’m anticipating that this experiment will be interesting and relatively challenging because a thermistor is a type of resistors whose resistance changes significantly when its temperature changes, consequently a slight variation in temperature can lead to a vast change in the resistance, therefore I have to be extremely accurate when calculating the temperature as a mistake or inaccurate reading on the thermometer will affect my results considerably.

I will be using a bead thermistor with a negative temperature coefficient, which means the resistance decreases with an increase in temperature. The apparatus I will require will be a thermistor, a multimeter, two wires and crocodile clips. I will also need a beaker, a kettle and a thermometer.

image00.png

image01.png

As thermistors are thermally sensitive resistors known for exhibiting a large change in resistance with only a small change in temperature, they are considerably interesting and significant in industry. If a chip in a circuit overheats, its resistance falls, so more current passes through it.

...read more.

Middle



I must keep the surrounding room temperature the same or the particles in the wire will move faster (if the temperature is increased) and this will therefore have an effect on the resistance. The cross sectional area of the wire must be kept constant throughout as well.

The material of the wire must also be kept the same as different materials have different conductivity.

Also for the thermistor experiment, I must also keep the surrounding room temperature constant, the cross sectional area and the wire material constant for the same reasons as above.

To get an accurate reading on the thermometer which is going to be used, the depth of water must be at least 7cm, therefore I will need at least 7cm of water in my beaker to avoid inaccurate thermometer readings.


For the first experiment, the apparatus will be set up as above and the multimeter will be set on resistance.  The water will then be heated using a kettle (a Bunsen burner etc. could also be used) but I felt a kettle would be safer. A thermometer will record the temperature of the water which is to be poured into the beaker. The thermistor will then be complete submerged in the water. The results will be recorded.

...read more.

Conclusion

As stated earlier, as a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. In fact resistance, in ohms is equal to the electromotive force or potential difference, in volts divided by the current, in amperes.

I feel that overall the results were quite accurate. This can be seen when we look at the graphs, which shows a relatively straight line with all of the points apart from one being very close to or on that line.


Wire temperature and may have affected some results, also the material of the wires may not be as pure as it should have been. The main reason for this was probably due to the equipment that we used being inaccurate. To extend the investigation, I could have used a different resistor, or changed the cross sectional area of the wire.


...read more.

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

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Investigate how the temperature affects the resistance of a thermistor.

    A thermistor is a semi-conductor. Semi-conductors have a small gap and although there are not many electrons flowing through the conduction band as the potential difference increases in a circuit (along with the temperature in the semi-conductor) more energy is going into the valence band.

  2. Experiments with a thermistor

    It remained constant from the 14.0cm onwards because the change in resistance of the thermistor was quite tiny, and therefore it could not be detected by the multi-meter. Error Report * I could not position the thermistor any closer to the candle than 4cm; otherwise it would melt due to the high temperature.

  1. Investigate the relationship between temperature and resistance in a thermistor.

    To calculate the resistance in the next experiment I will also measure the Voltage using a voltmeter. I need to do this because although I am keeping the voltage the same on the power pack this may not be accurate due to the change in resistance round the circuit.

  2. The effect of temperature on the resistance of a thermistor

    8.10 1.23 0.15 50c 1) 11.03 1.17 0.11 0.11 2) 11.11 1.18 0.11 60 1) 15.22 1.13 0.07 0.07 2) 15.24 1.13 0.07 70 1) 20.01 1.05 0.05 0.05 2) 20.09 1.04 0.05 80 1) 1 0.98 - - 2) 1 0.99 - 90 1) 1 0.91 - - 2) 1 0.93 - 100 1)

  1. Characteristics of Ohmic and non-Ohmic Conductors.

    Thus the resistance decreases. Let me explain this theory using energy bands: Semiconductors have a narrow forbidden band between the valence and conduction bands. At normal temperature, the thermal energy of some valenc electrons, is sufficient for them to reach the conduction band, where they may become conduction electrons.

  2. Investigating the effect of 'length' on the resistance of a wire

    If the resistivity of a material is known, the resistance of a given length of material of known area of cross-section can be calculated. Prediction: As shown by the behaviour of resistors, when the length of the conducting wire increases, the further the electrons have to travel and so the

  1. Investigation into how the resistance of a thermistor varies with temperature.

    * R1 = the resistance with one battery. * R2 = the resistance with two batteries. * R3 = the resistance with three batteries. * R average = the average resistance for this temperature. Temperature V1 V2 V3 I 1 I 2 I 3 26� 1.6 3.1 4.5 3.4 7.0

  2. The aim of my investigation is to determine the specific heat capacity of aluminium.

    This was to determine whether the insulation was sufficient or whether some heat was actually being lost into the surroundings. Safety: * Do not touch the heated filament, as this is very hot. * Do not touch the aluminium block when the experiment is in operation as this to can also be hot.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work