Q.What are the advantages and disadvantages of AC over DC ?

AC's ability to be transformed to any voltage makes long-distance transmission efficient and its generators/motors simpler, but it cannot directly perform DC-only tasks like electrolysis or battery charging, and poses greater shock hazard at a given peak voltage.

Advantages of AC over DC

1. AC voltage can be stepped up or down easily and efficiently using a transformer, which has no moving parts and very high efficiency; this allows electrical power to be transmitted at very high voltage (hence low current, low $I^2R$ loss) over long distances and then stepped down for safe local use — DC cannot be transformed this simply.
2. AC generators (alternators) are simpler in construction, cheaper, and more robust than DC generators (which need a commutator and brushes that wear out and cause sparking).
3. AC motors (especially induction motors) are simpler, cheaper, more reliable, and need less maintenance than DC motors.
4. AC can be easily converted to DC (using rectifiers) when DC is needed, but the reverse (DC to AC) needs comparatively more complex inverter circuitry.

Disadvantages of AC compared to DC

1. AC cannot be used directly for processes that need a steady unidirectional current, such as electroplating, electrolysis, or charging storage batteries — it must first be rectified to DC. …