Dielectric breakdown is a critical concept in understanding the limitations of parallel plate capacitors. It occurs when the electric field within the capacitor becomes so strong that it causes the dielectric material to become conductive, leading to a rapid increase in current and potential capacitor failure. This phenomenon is significant because it sets a limit on the maximum voltage that can be applied across a capacitor for a given dielectric. The strength of the electric field causing breakdown is known as the dielectric strength, measured in volts per metre (V/m). Each dielectric material has its own dielectric strength, determining how much voltage the capacitor can handle before breakdown occurs. In practical applications, capacitors must be operated well below their dielectric breakdown voltage to ensure reliability and longevity. Engineers must carefully select dielectric materials based on their dielectric strength, especially in high-voltage applications, to prevent capacitor failure and ensure the safety and efficiency of electronic devices.

Temperature has a significant impact on the performance of parallel plate capacitors. Primarily, it affects the dielectric material's properties within the capacitor. Most dielectrics are sensitive to temperature changes, which can alter their dielectric constant (εr). As the temperature increases, the dielectric constant typically decreases, leading to a reduction in the capacitor's capacitance. This is because higher temperatures can increase the thermal agitation of the molecules within the dielectric, potentially disrupting their alignment in the electric field and thereby reducing the material's ability to store electrical charge. Additionally, temperature variations can cause physical expansion or contraction of the capacitor's materials, potentially affecting the distance between the plates (d) and thus the capacitance. In designing and using capacitors, particularly in temperature-sensitive applications, it is crucial to consider these effects. Capacitors must be chosen and utilised within their specified temperature ranges to ensure accurate performance and prevent damage or degradation over time.

The presence of a dielectric in a capacitor does indeed increase the maximum charge the capacitor can hold. This is due to the dielectric's effect on the capacitor's capacitance. When a dielectric material is inserted between the plates of a capacitor, it increases the capacitance of the capacitor, as the relative permittivity (εr) of the dielectric material is greater than 1 (the permittivity of a vacuum). Since capacitance (C) is defined as the ratio of the charge (Q) stored to the potential difference (V) across the plates (C = Q/V), a higher capacitance means that for a given voltage, the capacitor can store more charge. The dielectric achieves this by reducing the electric field strength between the plates, allowing more charge to accumulate without increasing the voltage. Therefore, using a dielectric material in a capacitor is a common and effective way to increase its charge storage capacity without needing to increase its size or the voltage applied.

The dielectric constant (εr) plays a pivotal role in the design of capacitors for specific applications. The dielectric constant is a measure of a material's ability to increase the capacitance of a capacitor compared to the same capacitor with a vacuum between its plates. A higher dielectric constant means that the material can store more electric field energy, which translates to a higher capacitance for the same size and plate separation. This is particularly important in applications where space is limited but high capacitance is required, such as in compact electronic devices. Additionally, different dielectric materials have varying properties such as temperature stability, dielectric strength (maximum electric field the material can withstand without breaking down), and cost. These factors must be considered alongside the dielectric constant when designing capacitors for specific applications. For instance, capacitors for high-frequency applications might require dielectrics with low loss tangent values, whereas those for high-voltage applications need materials with high dielectric strength. The choice of dielectric material and its dielectric constant is thus a key decision in capacitor design, impacting the capacitor's performance, application suitability, and overall efficiency.

The distance between the plates in a parallel plate capacitor is crucial for several reasons. Firstly, it directly affects the capacitance of the capacitor, as capacitance is inversely proportional to the distance between the plates (C = Aε₀εr/d). A smaller distance between the plates results in a higher capacitance, allowing the capacitor to store more charge for a given voltage. However, reducing the distance also brings the plates closer to each other, increasing the risk of electrical breakdown, especially at high voltages. This is because a smaller gap reduces the dielectric strength, the maximum electric field the dielectric material can withstand before becoming conductive. Therefore, there is a trade-off between achieving high capacitance and maintaining operational safety and reliability. In high-voltage applications, a larger distance might be necessary to prevent breakdown, while in applications where size is a constraint, a smaller distance may be preferred to achieve higher capacitance. The choice of plate distance is thus a critical design consideration, balancing the desired capacitance, the operational voltage range, and the physical dimensions of the capacitor.