Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

In capacitive circuit, the voltage and current are out of phase. the current leads the voltage by 90 degrees. this can be explained by these two equations:

$$V = V_{\max} \sin \omega t$$

$$I = I_{\max} \cos \omega t.$$

Now, my question is that what does this statement mean physically that "current leads the voltage by 90 degrees? It is clear mathematically that if $V = 0$ then $I$ is maximum but how do we explain this physically? hope you understood my question

share|improve this question
add comment

1 Answer

Capacitor charge $q$ is just the accumulation of the current $i$ into the capacitor:

$$ q = \int i \, dt \quad \text{or} \quad i = \frac{dq}{dt} $$

So, starting with an uncharged capacitor, a current $i$ does not instantaneously lead to a charge $q$; instead charge builds up with time, lagging the current. The formulas you quoted are direct consequences of this behavior.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.