Physicists claim that charge never flows through an ideal capacitor. Yet when an uncharged capacitor is first placed in series with a resistor and a battery, then current flows through the battery and the resistor. Explain how this is possible.
Plus charges flow to one side, minus charges to the other.
To understand how current flows through a capacitor initially, we need to consider the behavior of charges and the role of the electric field.
1. At the beginning of the process, a charged capacitor is unconnected. It consists of two conductive plates separated by an insulating material called a dielectric. These plates have equal but opposite charges, resulting in a zero net charge.
2. When an uncharged capacitor is connected in series with a resistor and a battery, an electric field is established across the capacitor plates due to the potential difference provided by the battery. This electric field creates an electrostatic force that attracts charges from one plate of the capacitor towards the other.
3. As the charges start moving, current flows through the wire in the circuit and the resistor, creating a temporary flow. However, it's important to note that during this initial phase, the charges don't actually cross the insulating dielectric inside the capacitor. Instead, they accumulate on the surface of the plates closer to the wires leading to the battery.
4. The accumulation of charges on the surface of the capacitor plates creates a potential difference across the capacitor. This potential difference gradually increases as more charge accumulates on the plates.
5. The rate of charge accumulation on the plates depends on the capacitance of the capacitor. The capacitance determines how much charge the capacitor can store per unit of potential difference.
6. As the accumulation of charges continues, the potential difference across the capacitor reaches a point where it matches the potential difference provided by the battery. At this stage, equilibrium is achieved, and the movement of charge through the circuit stops. The capacitor is fully charged, and no further current flows through it.
In summary, current flows through the battery and the resistor because charges accumulate on the surface of the capacitor plates in response to the electric field created by the battery. However, during this process, charge does not actually cross the insulating dielectric of the capacitor. Once the capacitor reaches its full charge, no current flows through it, as the potential difference across the capacitor matches that of the battery.