Analog Electronics
A diode is electricity’s one-way gate — like the valve on a bicycle pump: air goes in but cannot come back out. It passes current only from anode to cathode, and a small "entry fee" is charged across it: ~0.7 V in silicon.
AC is current that keeps reversing direction; most devices, however, want one-way DC. A single diode passes only the positive half of the AC (half-wave). A four-diode bridge also "folds up" the negative half (full-wave) — the gaps shrink by half and the transformer is used twice as efficiently.
The rectified wave is still bumpy. A filter capacitor works like a water tank: it fills at the peaks and feeds the load through the valleys. The remaining fluctuation is called ripple: ΔV ≈ I/(f·C) — a bigger tank (C) or more frequent refills (f) → smoother DC.
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