Question

Which of the following can be used in the output circuit of a diode rectifier to filter ac ripples?

• A. A capacitor in series with the load
• B. An inductor in parallel with the load
• C. A capacitor in parallel with the load
• D. Both capacitor and inductor in parallel with the load
• E. Both capacitor and inductor in series with the load

Hint:

Standard filters: Capacitor = Parallel; Inductor = Series. Remember "C is for Cross (Parallel)" and "L is for Line (Series)".

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The output from a diode rectifier is pulsating DC (it contains AC ripples superimposed on a DC level). Filters are used to smooth this out.
Step 2: Key Formula or Approach:
Recall theoretical facts about electrical filters:
Capacitors oppose changes in voltage and act as a low-impedance path to AC ripples while blocking DC. Thus, they must be placed in parallel to shunt the ripple away from the load.
Inductors oppose changes in current and act as a high-impedance path to AC. Thus, they must be placed in series with the load to block ripples.
Step 3: Detailed Explanation:
Let's evaluate the standard placements:
(A) Capacitor in series: This would block the desired DC output completely.
(B) Inductor in parallel: This would short out the desired DC output.
(C) Capacitor in parallel: It stores charge when voltage rises and releases it when voltage drops, smoothing the voltage across the load. It shunts the AC ripple component to ground. This is the correct standard arrangement.
(D) Both in parallel: The inductor would short the DC.
(E) Both in series: The capacitor would block the DC.
Step 4: Final Answer:
A capacitor in parallel with the load can be used.