When AC flows through components, it behaves differently than DC. In addition to standard resistance, circuits containing inductors and capacitors offer a frequency-dependent opposition to current known as reactance. When these components are combined in an LCR series circuit, they can exhibit a phenomenon called resonance. At a specific resonant frequency, the inductive and capacitive reactances cancel each other out, maximizing the current. This principle is fundamental to how radios and televisions tune into specific station frequencies.
Ultimately, understanding AC involves analyzing the phase relationships between voltage and current, calculating the effective (RMS) values of power, and utilizing transformers to safely deliver usable electricity to our appliances.