# Homework Help: Conceptual Question-Capacitance

1. May 7, 2017

### PlatoDescartes

1. The problem statement, all variables and given/known data
We start with a 2.50 μF capacitor connected to a power supply set to a voltage of 9.30 V. Then we increase the voltage on the power supply by 3.00 V. Now what is its capacitance?

2. Relevant equations
Q=ΔV*C

3. The attempt at a solution
The answer is 2.5 μF still, but WHY doesn't the capacitance change when the voltage changes?

2. May 7, 2017

### phinds

Why do you think it should? If you had a 10 ohm resistor across the power supply would you expect it to become 11 ohms if you increased the voltage?

3. May 7, 2017

### PlatoDescartes

According to the equation Q=VC, if voltage increases, capacitance should too... I'm missing something here.... I apologize!

4. May 7, 2017

### PlatoDescartes

Capacitance is not dependent on voltage nor charge though, only material/geometry. Which is why it doesn't change.

5. May 7, 2017

### magoo

Q is the charge.

If you increase the voltage (V), the charge increases but the capacitance (C) stays constant.