# Why capacitor allows AC to flow through it and blocks DC?

**URL:** <https://forumautomation.com/t/why-capacitor-allows-ac-to-flow-through-it-and-blocks-dc/9890>\
**Category:** Electrical\
**Tags:** capacitance\
**Created:** [October 2, 2021, 4:30am UTC](https://forumautomation.com/t/why-capacitor-allows-ac-to-flow-through-it-and-blocks-dc/9890 "2021-10-02T04:30:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![instrumentationtechi](https://forumautomation.com/letter_avatar_proxy/v4/letter/i/50afbb/32.png) [@instrumentationtechi](https://forumautomation.com/u/instrumentationtechi)\
**Post date:** [October 2, 2021, 4:30am UTC](https://forumautomation.com/t/why-capacitor-allows-ac-to-flow-through-it-and-blocks-dc/9890/1 "2021-10-02T04:30:00Z")

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Explain why an AC current can flow through the capacitor and why capacitor blocks DC

 ![1](https://cdn.forumautomation.com/original/2X/9/9ae5bc5d34a2e00e390e229fad19db14ba390a46.jpeg)

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**Author:** ![ashlin](https://forumautomation.com/user_avatar/forumautomation.com/ashlin/32/3775_2.png) [@ashlin](https://forumautomation.com/u/ashlin)\
**Post date:** [October 2, 2021, 4:33am UTC](https://forumautomation.com/t/why-capacitor-allows-ac-to-flow-through-it-and-blocks-dc/9890/2 "2021-10-02T04:33:32Z")

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The capacitor blocks DC current in a circuit, whereas AC current is being passed. This explains by the reactance of a capacitor (x) = 1/(2_pi_f\*C). Capacitor reactance is highly dependent on the frequency of the AC voltage. DC current is constant = 0

AC current does not have direction. No impedance. AC current bypasses resistance!