Why shouldn't electrolytic capacitors be used in an AC circuit?

• A. They are polarized, and they pass current of one polarity and block the opposite.
• B. They have higher voltage ratings than needed.
• C. They are non-polarized and cannot handle AC.
• D. They store energy in magnetic fields causing core saturation.

Answer: (A)

In AC circuits, voltage polarity reverses every half cycle. Electrolytic capacitors are polarized devices designed to operate with a specific polarity, having a positive and a negative terminal. When the voltage reverses, the reverse bias can damage the dielectric oxide layer, causing increased leakage, heating, venting, or even catastrophic failure. That makes them unsuitable for AC unless you use a non-polarized alternative or arrange components to handle the alternating direction.

Higher voltage rating doesn’t address reverse polarity risk, so that doesn’t solve the problem. The claim that electrolytics are non-polarized is incorrect—these parts are inherently polarized. And capacitors store energy in an electric field, not a magnetic one, so the statement about magnetic core saturation doesn’t apply. For AC use, non-polarized capacitors (like film or ceramic) or back-to-back arrangements of polarized capacitors are preferred.