In a purely resistive AC circuit, the current and the voltage are
- A. in phase with each other
- B. 90 degrees out of phase, with current leading
- C. 90 degrees out of phase, with current lagging
- D. 180 degrees out of phase
Explanation
A resistor obeys Ohm's law at every instant, so the current peaks exactly when the voltage peaks and both pass through zero together. Phase differences appear only when capacitance or inductance is present. Because they are in phase, all the power in a resistive circuit is dissipated as heat.