Which statement correctly distinguishes energy from power?

• A. Energy is the rate of doing work; power is the total amount of work done.
• B. Energy is the capacity to do work; power is the rate at which work is done.
• C. Energy is measured in Watts; power is measured in Joules.
• D. Energy is only kinetic; power is only potential.

Answer: (B)

Energy is the capacity to do work, while power is the rate at which work is done. Energy is the stored ability to cause change—like the chemical energy in fuel or gravitational potential energy—whereas power tells you how fast that energy is used or transferred to do work. In units, energy is measured in joules and power in watts, with 1 watt equal to 1 joule per second. This means you can have a large amount of energy but deliver it slowly (low power) or rapidly (high power). Describing energy as the rate of doing work would confuse it with power, and describing power as the total amount of work would mix up rate with quantity. Energy isn’t limited to kinetic form, and power isn’t limited to transforming only potential energy; power simply reflects the speed of energy transfer, whatever form the energy takes.