Electricity and Magnetism

Chapter 45

Power Dissipation in RCL AC Circuits

Prior to our conducting a rigorous analysis of the flows of power in RCL circuits driven by

an AC source, let’s think heuristically about the physics.

R The current that flows in the circuit dissipates energy as it passes through the

resistive element. [Recall that this conversion of electromagnetic energy into thermal

energy is called Joule heating.]

C The current flowing in the circuit deposits charge onto the capacitor until its

stored energy reaches a maximum value of U

E

=

1

2

C V

2

0

. The potential drop

across the capacitor is maximised

1

at the same instant[s] as the charge. When the

voltage drop across the