What are the primary considerations when selecting the size of electric cable?

The selection of the size of electric cable is heavily influenced by current-carrying capacity and allowable voltage drop, making this the correct answer. Current-carrying capacity refers to the maximum amount of electrical current a cable can safely carry without overheating. It's essential to select a cable size that can handle the expected load to prevent potential overheating, which could lead to insulation failure or fire hazards.

The allowable voltage drop is another crucial factor. As electricity travels through a conductor, some energy is lost in the form of heat due to resistance, leading to a drop in voltage. Ensuring the voltage drop remains within acceptable limits is vital to maintain the efficiency of electrical power distribution. If the voltage drop is too high, it can adversely affect the performance of electrical equipment.

Other considerations like voltage and frequency, total resistance and insulation type, as well as cable length and installation method, do play a role in the overall system design but are secondary to the primary considerations of current capacity and voltage drop when determining the appropriate cable size. This is because, while they can influence other factors like cable performance and safety, they do not directly address the fundamental requirements needed to safely and effectively transmit electrical power over the desired distances.