# How large current is needed to get a voltage change over a capacitor?

First off, this is question from my homework.

I'm not sure I understand the question, wouldn't the needed current be > 0?

• You need charges for the voltage to change. Charge = Current * time. So any non-zero current applied for a non-zero time will change the voltage. – JimmyB Oct 7 '16 at 12:18
• @Viktor: Edit your question to include the whole text of your question. There's got to be more than you have given us. Then show how you have tried to solve it so far. – Transistor Oct 7 '16 at 12:24
• No, really, this is it. The headline is Theory questions. – Viktor Oct 7 '16 at 12:25

Two equations to consider with Capacitors

1. Q = CV
2. $I = C\frac{\Delta V}{\Delta t}$

Likewise

1. Q = It

For there to be a voltage across a capacitor which was initially 0V, there must be a charge flow. How much voltage in a given time would dictate the current required.

• Does the current needed depend on the voltage over the capacitor? – Viktor Oct 7 '16 at 12:30
• Current through a capacitor is never dependent on the voltage, ,only on the rate of change of voltage, like JonRB already said: I=Cdu/dt. – Bart Oct 7 '16 at 12:33