What is the purpose of the filter in a linear power supply?

In a linear power supply, the alternating current (AC) first passes through a transformer and then a rectifier, which converts the AC into pulsating direct current (DC). At this stage, the current is flowing in one direction but is rising and falling rapidly in a wave-like pattern. The purpose of the filter, which typically consists of large capacitors and sometimes inductors (chokes), is to smooth out these pulsations. It stores energy during the peaks of the pulses and releases it during the valleys, resulting in a much steadier, flatter DC output. Common distractors represent other stages of the power supply. Converting AC to DC is the job of the rectifier, while keeping the voltage constant under heavy load is the responsibility of the voltage regulator.