The capacitance of a parallel plate capacitor changes when a dielectric is inserted between the plates. This is mainly due to the dielectric material's ability to influence the electric field and store electric charge.
When a dielectric is inserted between the plates of a parallel plate capacitor, it affects the capacitance of the capacitor in the following ways:
1. Dielectric constant (k): The dielectric material has a property called the dielectric constant or relative permittivity (k). It is a measure of how well the dielectric can store electric charge compared to a vacuum or air. The dielectric constant is always greater than 1, indicating that the dielectric material enhances the capacitance of the capacitor.
2. Electric field strength: When the dielectric is inserted, it reduces the electric field strength between the plates. The dielectric material contains atoms or molecules that can align themselves with the electric field, reducing the net electric field and allowing more electric charge to be stored on the plates.
3. Polarization: The dielectric material also undergoes polarization, where the positive and negative charges within the dielectric align themselves with the applied electric field. This alignment creates an opposing electric field that reduces the overall electric field between the plates. As a result, more charge can be stored on the plates, leading to an increase in capacitance.
Overall, the presence of a dielectric material between the plates of a parallel plate capacitor increases the capacitance by enhancing the ability of the capacitor to store electric charge. The dielectric constant, electric field strength, and polarization all contribute to this increase in capacitance.