# Investigating the effect of resistance on a capacitor circuit.

Investigating the effect of resistance on a capacitor circuit

Method: We will set up the following circuit. We will measure the capacitor pd. (Vc) with the cell connected.

Then we will remove the cell and connect point A to point B, at the same moment starting a stopwatch. We will record the length of time (t) for the Vc  to decay to 3.75 Volts. We intend to repeat this procedure using different resistors.

Conclusion:

From the graph we can clearly see that the time taken for the capacitor to discharge is directly proportional to the resistance. This is because the graph shows a definite straight line going through or near most of the points. This means that the higher resistor you use the longer it will take for the capacitor to discharge. The experiment has therefore proved the prediction correct i.e. the resistance should be directly proportionate to the time taken for the capacitor to de-charge. This can be explained by the following: Capacitors store electrical charge. When current is passing through the circuit the capacitor charges up as the current can't jump between the gap of the two plates but charge is held there because of the force of the opposite poles. This means that more and more electricity is stored until it reaches its full capacity. But when the circuit is broken the capacitor de-charges releasing electricity through the circuit. The resistor slows down the current causing 'congestion' and means that the capacitor has to de-charge slower because only a limited amount of charge can travel through a circuit with a high resistance at any one given time.

Evaluation:

The method was a good way of carrying out the experiment as it was quite easy to conduct once the circuit was connected, the results seem to be fairly accurate and the obtaining of results was systematic. However it would have been better to use two people conducting the experiment as one would to connect point A to point B while the other partner would start the stopwatch. Also the experiment took extremely long due to the high resistances in some cases like the 680kΩ experiment. Instead we should have used lower resistances, this would also have made ...