[Rapier 141]

Just a question about constructing circuits for capacitors:
If asked to put together a circuit with a capacitor, ammeter, voltmeter, resistor and wires - how would u go about this and how would u work out things out like capacitance and energy stored. Cheers

Also, are there any bits in particular i shud be revising for 2morro?

[figureeight]

Revise your entire syllabus, that's the only advice I can give. It's not a hint, just a general tip.

You would place all of the components in series, apart from a voltmeter, which should be placed across the capacitor. This circuit will allow you to charge and measure the current to the capacitor, and to discharge it, you will need to either short circuit the capacitor (to discharge it immediately) or the battery (to measure the rate of discharge). You'll need a stopwatch too.

Measure:

Capacitance (need a variable power supply) - you'll need to take measurements of I and t as you charge the capacitor, say every 20 seconds until 3 minutes has passed. Draw an I-t graph for each voltage, from 0V to 15V going up in 3V gaps. Measure the voltage each time across the capacitor after the 3 minutes is over, and note it down, as the voltage on your power supply could be different to the actual voltage in the circuit.

Find the area under each I-t graph (there should be 6 graphs, and the areas under each one represents the charge stored). Then, collate your charge and voltage measurements, and plot them in a Q-V graph. It should be linear, through the origin and the gradient should be the capacitance of the capacitor.

Energy stored - this is the area under said Q-V graph.