Power lines carry energy in the form of electricity.

Electrical

Explanation:

"Power lines or transmission lines, such as those in Figure 1, move electricity from point A to point B. Usually, this electricity is alternating current so step-up transformers can increase the voltage. This increased voltage allows efficient transmission for 500 kilometers or less. There are 3 types of lines:[3]

Overhead lines are very high voltage, between 100 kV and 800 kV, and do the majority of long distance transmission. They must be high voltage in order to minimize power losses to resistance.

Underground lines are used to transport power through populated areas, underwater, or pretty much anywhere that overhead lines can't be used. They are less common than overhead lines due to heat-related losses and higher cost.

Subtransmission lines carry lower voltages (26 kV - 69 kV) to distribution stations, and can be overhead or underground." - University of  Calgary ENERGY EDUCATION: ELECTRICAL TRANSMISSION.

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.