Is it correct to say that the higher the dielectric constant, the stronger the insulation ability? What is the relationship between dielectric constant and dielectric breakdown strength? The dielectric constant, also called the dielectric constant, dielectric coefficient, or permittivity, is a coefficient that characterizes insulation ability, denoted by the letter ε, with the unit of farad per meter (F/m). It is defined as the ratio of electric displacement D to electric field strength E, ε = D/E. The unit of electric displacement D is coulomb per square meter (C/m^2). When a capacitor plate is filled with a substance with a relative dielectric constant ε, the capacitance increases by a factor of ε. Therefore, the relative dielectric constant εr can be measured as follows: first, measure the capacitance C0 of the capacitor when the space between its two plates is vacuum. Then, using the same distance between the capacitor plates but with a dielectric added between the plates, measure the capacitance Cx. Then, the relative dielectric constant can be calculated using the formula εr = Cx/C0. The voltage that causes the dielectric to break down. Under a sufficiently strong electric field, the dielectric will lose its dielectric properties and become a conductor, which is called dielectric breakdown, and the corresponding voltage is called breakdown voltage. The electric field strength at which dielectric breakdown occurs is called breakdown field strength. Different dielectrics have different breakdown field strengths at the same temperature. When the dielectric of a capacitor and the distance d between the two plates are fixed, from U1-U2 = Ed, the breakdown field strength determines the breakdown voltage. The breakdown field strength is often also called the dielectric strength of the dielectric. The key factor in improving the voltage withstand capability of a capacitor is the dielectric strength of the dielectric. The attached table shows the relative dielectric constant εr and dielectric strength of various dielectrics. Dielectric εr Breakdown field strength, ×10^6/(V·m^-1). The insulation of a substance mainly examines the dielectric constant and dielectric loss factor; these two constants determine the strength of the breakdown voltage. For a simple example, substance A is a cyanate ester resin. Suppose it is L cm long, and high voltage is connected to both ends of the substance. To break it down, the required field strength is εr, ×10^6/(V·m^-1). Also, theoretically, "the larger the dielectric constant, the better the insulation" is correct. The larger the dielectric constant, the greater the insulation, but insulation must consider many other conditions, such as voltage level, air humidity. If the voltage level is high and air humidity is high, the air may be broken down and ionized to conduct electricity. The dielectric constant only explains the conductivity from one aspect! The dielectric constant of air is close to 1, and only in a vacuum is it exactly 1. Why it is 1 can be proven by strict mathematical derivation. The dielectric constant of ammonia gas is very large, but the factor of water is not considered.
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