Alternating Current

Mr Rahul Kumar Singh

2026年7月 · Class 12 Physics Master Series 第 7 冊 · Rahul kumar singh

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While direct current (DC) flows steadily in one direction, Alternating Current (AC) periodically reverses its direction and changes its magnitude continuously with time. This is the form of electrical energy that powers our homes, offices, and heavy industries. The primary reason AC is preferred over DC for large-scale power distribution is efficiency; its voltage can be easily stepped up or down using transformers, minimizing energy loss as heat over long-distance transmission lines.

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.