I thought that capacitors will only act as a conductor while is is being charged and once fully charged it will not conduct any more. I know that current does not actually pass through the capacitor due to the plate between the insulator between the two plates but I use the word 'conduct' here for simplicity.
At low frequencies and DC currents the capacitor gets fully charged very early at the beginning of the cycle and acting afterward as an open circuit until the voltage drops in the second half cycle below the capacitor voltage when the capacitor starts to discharge. As a result the capacitor in the HP filter will will block low frequencies.
Also at high frequencies there is less electricity in the cycle so the capacitor does not get fully charged and it is always either charging and conducting or discharging so the current is not blocked at all and the capacitor is acting as a short circuit. As a result in HP filter high frequencies will pass.
Now if the capacitor receives two signals at the same time, the first has very low frequency and the other has very high frequency, the first will cause the capacitor to be fully charged so not allowing any more current to pass.
How the high frequency signal will pass now?
Will it actually pass?