AC Circuits

Induction is the process in which an emf is induced by changing magnetic flux, such as a change in the current of a conductor.

An RL circuit consists of an inductor and a resistor, in series or parallel with each other, with current driven by a voltage source.

Response of an RLC circuit depends on the driving frequency—at large enough frequencies, inductive (capacitive) term dominates.

In a circuit with a resistor and an AC power source, Ohm's law still applies (V = IR).

The voltage across a capacitor lags the current. Due to the phase difference, it is useful to introduce phasors to describe these circuits.

In an AC circuit with an inductor, the voltage across an inductor "leads" the current because of the Lenz' law.

Resonance is the tendency of a system to oscillate with greater amplitude at some frequencies—in an RLC series circuit, it occurs at $\nu_0 = \frac{1}{2\pi\sqrt{LC}}$.

Power delivered to an RLC series AC circuit is dissipated by the resistance in the circuit, and is given as $P_{avg} = I_{rms} V_{rms} cos\phi$. Here, $\phi$ is called the phase angle.