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# A2 Physics coursework about capacitors help Watch

1. So the objectives of the coursework are:

-
• You will be given a capacitor whose capacitance is 470x10^-6 F according to the manufacturer. You are to charge it and then discharge it through a resistor of your own choosing.
• ...also calculate the capacitance C of the capacitor that you have found from your experiment...

What we do in the experiment, is we set up a capacitor charge/discharge circuit, charge the capacitor up instantly, and then discharge it through a resistor and take readings of how much voltage there is across the capacitor in different time intervals. I think at least 10 readings must be taken to be on the safe side. I know about plotting ln V against t graph, finding gradient and all that stuff.

One problem I want to make sure of is, assuming the capacitor is 470uF, I think I can choose the best resistor for me which can discharge the capacitor in an appropriate amount of time (5 mins around), so 10 recordings can be taken.

** I just want to make sure what I am thinking is right, if not, please try to tell me what is wrong **

using the equation V = v x e^(-t/RC), and every e^(-1), the capcitor discharges 0.38 of the initial voltage every value of RC. v is the initial, V is the voltage after..

the highest power supply i am given is 6V, so i will use that. so if I decide to use a 200,000 ohms resistor.. the value of RC will be 200,000 ohms times 470 x 10^-6, which is 94 seconds. 0.38x6V = 2.28V. So 2.28Volts will be discharged every 94 seconds. therefore, all 6V will be discharged in 256 seconds, which is 4:15 close enough to 5 minutes. Is my thinking here right?
2. bump..

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Updated: January 17, 2015
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