Physics A2 · Alternating currents. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Rectification changes alternating current into direct current, which flows one way only. A diode does this because it conducts in one direction only.
One diode in series with the load gives half-wave rectification: one half of each cycle passes and the other half is blocked, leaving gaps. A bridge rectifier of four diodes gives full-wave rectification. In each half-cycle a different pair of diodes conducts, so the current in the load is always in the same direction and there are no gaps.
The output still rises and falls. A capacitor in parallel with the load gives smoothing: it charges near each peak and then discharges slowly through the load, holding the p.d. up.
Students say a smaller load resistance gives better smoothing. A smaller resistance draws more current, so the capacitor discharges faster and the ripple gets bigger.
Answer: About 8.8 V (a ripple of about 0.2 V)
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