Electronic – Voltage drop across capacitor in a DC circuit? (Simple question)

capacitorcircuit analysisvoltage

I'm trying to find the voltage drop across a capacitor in a DC circuit. We can assume that the capacitor is fully charged and in a steady state. Therefore, the capacitor is now an open circuit. So this is really an open circuit voltage problem.

My question concerns the following section of the circuit:

Node a -> resistor -> node b -> capacitor -> ground

Is the voltage at node b zero because no current flows through the capacitor \$(V=0R)\$? Or does the voltage at node b equal voltage at node a?

Circuit

Best Answer

The voltage across a resistor is proportional to the current thru it. When there is no current thru a resistor, the voltage across it is therefore zero. Since the voltage across the resistor is zero, the voltage of the two nodes at either end are at the same potential.