1 Answer
A capacitor is like a storage device for electric charge, and it has two plates separated by an insulating material called a dielectric. Now, when you apply a DC (Direct Current) voltage across the capacitor, something interesting happens.
At first, when the DC voltage is applied, the capacitor starts charging up. The electric field between the plates grows as charge builds up. However, after some time, once the capacitor is fully charged, the voltage across its plates becomes equal to the applied DC voltage. At this point, the current stops flowing because the capacitor now acts like an open circuit.
Here’s why DC can’t pass through once the capacitor is fully charged:
1. **Capacitor's Behavior with DC:**
A capacitor blocks DC after it is fully charged because a DC voltage doesn't change with time. For current to flow, the electric field (or voltage) has to change (like in AC), but a constant DC voltage doesn't cause the plates of the capacitor to keep charging or discharging once equilibrium is reached.
2. **Charging Process:**
Initially, when the DC voltage is first applied, current flows as the capacitor charges. This charging current decreases as the capacitor charges up and eventually stops completely when it reaches its full charge.
3. **Why no DC after that:**
Once fully charged, the capacitor essentially "stops" any further current from flowing through it because there’s no change in the voltage or the electric field to drive the current.
This is why capacitors are used in circuits to block DC and allow AC to pass through, as AC voltage changes direction and can continue to cause charging and discharging of the capacitor.
At first, when the DC voltage is applied, the capacitor starts charging up. The electric field between the plates grows as charge builds up. However, after some time, once the capacitor is fully charged, the voltage across its plates becomes equal to the applied DC voltage. At this point, the current stops flowing because the capacitor now acts like an open circuit.
Here’s why DC can’t pass through once the capacitor is fully charged:
1. **Capacitor's Behavior with DC:**
A capacitor blocks DC after it is fully charged because a DC voltage doesn't change with time. For current to flow, the electric field (or voltage) has to change (like in AC), but a constant DC voltage doesn't cause the plates of the capacitor to keep charging or discharging once equilibrium is reached.
2. **Charging Process:**
Initially, when the DC voltage is first applied, current flows as the capacitor charges. This charging current decreases as the capacitor charges up and eventually stops completely when it reaches its full charge.
3. **Why no DC after that:**
Once fully charged, the capacitor essentially "stops" any further current from flowing through it because there’s no change in the voltage or the electric field to drive the current.
This is why capacitors are used in circuits to block DC and allow AC to pass through, as AC voltage changes direction and can continue to cause charging and discharging of the capacitor.