DC block by capacitor

How capacitor blocks DC voltage and transmits AC voltage?

at low frequency the capacitive impedance is high where as at larger frequencies the capacitive impedance decreases.

that's y the dc is blocked by the capacitor

Between 2 plates of capacitor is the isolator, that stops the DC current.

In case of AC current, as it changes current flow directions alternatively, so the capacitor plates charge and discharge electrons continously, and the AC current likely goes through the capacitor.

capacitor consists of two plates and there is no direct path between them so a change of charge in one will be duplicated oppositely in the other,,.... which is not the case for DC.... so capacitor blocks DC....

this can be easily seen when looking at the impedance of a capacitor:
\[Z=\frac{1}{j{\omega}C}\]

(where \[\omega=2{\pi}f\])

as we see, the higher the frequency, the lower the impedance. This means that when the current changes from positive to negative in a fast way, it will find low resistance to it, so there won't be any problem in passing through.

on the other side, if the frequency is low (\[f{\approx}0\]) the impedance will be very high. The closer to zero, the impedance will be closer to infinity. This means that the current changing very slow, or even not changing (f=0) will find an obstacle when trying to pass through.

This is why it's common to understand a capacitor as a high-pass filter (when used in series, not in parallel)

hope this helps

capacitive reactance for dc is ininite hence it blocks and passes ac of low reactance.

The impedance of the capacitor is = 1/(JWC) where J: imaginary sign,w: frequency, and c: the capactiy of the capacitor.
as shown in the equation the impedance depends on the frequency, as known the frequency of DC is ZERO, so the impedance of the capacitor is infinte in DC.

use a HPF (High Pass Filter). where it will not allow low frequency to pass such as in DC. DC has a very low frequency which sometimes considered as zero to simplify computation or analysis. But in reality it is really hard to obtain that 0 freq.

since its reactance is inversely proportional to frequency ,it will block DC by poising a high impedance
case will reversed if it is inductor

Xc=1/2*pi*f*c, so when there is dc voltage this mean it has f=0hz so Xc will be infinite and it will e open for DC but for AC its not that case