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Overview
Power is the rate at which work is done or energy is transferred. Two machines may do the same amount of work, but the one that does it in less time has greater power.
Work Over Time
The basic power idea is work divided by time. If the same amount of work is completed in a shorter time interval, the power is greater.
Energy Transfer Rate
Power can also be understood as energy transfer rate. A motor, light bulb, engine, heater, or turbine can be described by how much energy it converts per second.
Units of Power
The SI unit of power is the watt. One watt equals one joule per second, showing that power is energy transfer per unit time.
Mechanical Power
In mechanical systems, power describes how quickly a force does work. When force and velocity act in the same direction, mechanical power can be related to force multiplied by speed.
Connection to Electrical Power
Power also appears in electricity. Electrical power measures how quickly electrical energy is transferred or converted by a circuit or device.
Power and Efficiency
Power and efficiency are related but different. Power measures rate, while efficiency measures how much input becomes useful output.
Common Mistakes
A common mistake is confusing power with energy. Energy is an amount, while power is a rate.
Applications
Power describes engines, motors, generators, appliances, athletes, vehicles, elevators, cranes, power plants, and electronic devices.
Why This Matters in Physics
Power explains why time matters in energy transfer and prepares students for machines, efficiency, electricity, and engineering performance.