Which material is commonly used as an insulator where conductors terminate at panels?

The material commonly used as an insulator where conductors terminate at panels is dielectric. Dielectric materials have the property of being electrical insulators, which means they do not conduct electricity, thereby preventing any unintended current flow. This is particularly important in applications involving electrical panels where conductors meet, as it helps to ensure safety and the integrity of the electronic components.

Dielectric materials are often specifically engineered to have high electrical resistivity and can withstand high voltages, making them ideal for electrical insulation. They can also serve other functions, such as reducing loss in capacitive components.

Other options, while they may have insulating properties to some extent, do not represent the primary choice in this context. Distance is not a material but rather a measurement, while plastic and rubber are generally recognized as insulators. However, dielectric materials are engineered for optimal performance in electrical systems, especially where high reliability is required.