Final answer:
The radius of the inner conductor in a coaxial cable used to carry electric power is mainly determined by the load current, but also takes into account the voltage and insulating material.
Step-by-step explanation:
When a coaxial cable is used to carry electric power, the radius of the inner conductor is primarily determined by the load current that the cable is expected to carry. This is because the diameter of the inner conductor affects its current-carrying capacity -- the larger the diameter, the higher the current-carrying capacity. However, the voltage and insulating material also influence the dimensions of the conductors, as they must be sized to safely contain the electric power within the specified voltage range and to withstand the electric field produced, without causing a breakdown in the insulating material.
It's important to note that while other factors such as overall size and load voltage do impact cable design, they are not the primary determinants of the inner conductor radius. Instead, these factors may influence the overall construction and materials used in the cable, as well as the thickness and type of insulation required.