why does capacitor blocks dc?

Answer 1

Electrons cannot easily pass directly across the dielectric from one plate of the capacitor to the other as the dielectric is carefully chosen so that it is a good insulator. When there is a current through a capacitor, electrons accumulate on one plate and electrons are removed from the other plate. This process is commonly called 'charging' the capacitor -- even though the capacitor is at all times electrically neutral. In fact, the current through the capacitor results in the separation of electric charge, rather than the accumulation of electric charge. This separation of charge causes an electric field to develop between the plates of the capacitor giving rise to voltage across the plates. This voltage V is directly proportional to the amount of charge separated Q. Since the current I through the capacitor is the rate at which charge Q is forced through the capacitor (dQ/dt), this can be expressed mathematically as:
I=dQ/dt=C(dV/dt) where
I is the current flowing in the conventional direction, measured in amperes
dV/dt is the time derivative of voltage, measured in volts per second.
C is the capacitance in farads


For circuits with a constant (DC) voltage source, the voltage across the capacitor cannot exceed the voltage of the source. (Unless the circuit includes a switch and an inductor, as in SMPS, or a switch and some diodes, as in a charge pump). Thus, an equilibrium is reached where the voltage across the capacitor is constant and the current through the capacitor is zero. For this reason, it is commonly said that capacitors block DC current.

Answer 2

Why Does Capacitor Block Dc

Answer 3

Basically a Capacitor consists of a dielectric in between its 2 conductive plates. as it is an an insulator, the electrons will not flow through this di-electric/insulator barrier. that's the reason for DC blocking by the Capacitor.

As it can be expressed in other way, " Capacitive reactance is inversely proportional to the frequency applied". Since DC has Zero freq, the reactance in "infinite". ( 1/2piFC).

Hope its clear to you now,

Praful.

Answer 4

because a capacitor in series charges to tha same potential as the dc voltage. with no potential difference electron flow stops.

Answer 5

Because at d.c. a capacitor is an open circuit.