Aim:
The aim of this investigation is to find out the relationship between resistance and conductive putty, and to see how length of putty affects this relationship.
The Experiment:
Conductive putty is specially designed to be a conductor; this is achieved by adding carbon black. This can easily be used to prove the concept of resistivity because it is malleable and so the cross-sectional area, length and shape can easily be changed.
This experiment will show the effects on resistance in a circuit, as the length of putty decreases.
I will be using 30cm of putty, and decreasing it by 5cm each time.
First the voltage of the battery will be taken using a voltmeter, and this will be recorded at the start of the experiment. Then a circuit will be constructed containing the battery, the ammeter and putty. See diagram. For each different length of putty, a reading will be recorded from the ammeter and when the practical has been completed, I will work out the resistance using the formula R=VI. From those results I will draw a graph and then evaluate and conclude my experiment.
Diagram:
Constants:
My constants include the weight of my putty – I am going to start each experiment with 50g of putty. I will also sustain the same thickness of putty throughout my experiment, and the same battery will be used constantly.
Variables:
Possible variables in this experiment are temperature, voltage, cross-sectional area, mass, surface area and length. My variable is going to be the length of my putty, which will decrease by 5cm each time. I am going to start each experiment, using 30cm of putty.