What is the measure of electric power when one amp flows at one volt?

When one ampere (amp) of current flows under a pressure of one volt, the measure of electric power is defined as one watt. This relationship comes from the formula for electrical power, which states that power (in watts) is equal to the voltage (in volts) multiplied by the current (in amperes). Therefore, using the formula P = V × I, if you have one volt and one ampere, the calculation yields one watt (1 W = 1 V × 1 A).

Understanding this concept is crucial for anyone in the field of utility arboriculture, as it relates to the energy management and safety when working near electrical systems. The other options represent different electrical quantities: ohms measure resistance, volts measure electrical potential, and joules measure energy. Each plays a distinct role in electrical systems, but in the context of power, watt is the correct unit.