# Homework Help: Show that Q is proportional to V for capacitor

1. May 29, 2012

### jsmith613

1. The problem statement, all variables and given/known data
Describe how you would show experimentally that the charge stored on a 220 µF capacitor is proportional to the potential difference across the capacitor for a range of potential differences between 0 and 15 V. Your answer should include a circuit diagram.

2. Relevant equations

3. The attempt at a solution

- charge the capacitor for a given Voltage, V
- ensure the capacitor is charging at a constant rate by varying the resistance of the variable resistor --> ensures current remains constant
- Q=It (current * time take for capacitor to charge)
- capacitor is charged when V on meter = V of supply
- Q/V = constant for range of values of V

Is this method correct - would it work?

p.s: I am aware my diagram is not very well drawn - i will obviously improve this in the exam

2. May 29, 2012

### truesearch

V is easy to measure....do you know of any way to measure Q?

3. May 29, 2012

### jsmith613

my syllabus only talks about coloumbmeters but the MS said the a coloumbeter would be insufficient for this experiment because the capacitance is too high.

I was simply wondering, would my method work?

4. May 30, 2012

### MalachiK

Your method sounds good to me - although it might be a bit tricky keeping the current constant unless the capacitor was charging very slowly.