Which unit is used to measure energy in heat energy problems?

• A. Joule
• B. Watt
• C. Newton
• D. Pascal

Answer: (A)

Energy is measured in joules in the SI system. In heat energy problems, the energy transferred as heat or as work is quantified in joules, because energy can be expressed as the amount of work done or heat transferred. A joule equals the work done when a force of one newton moves an object one meter in the direction of the force, or one newton-meter.

Watt is the unit of power, not energy, representing the rate of energy transfer per time. Newton is a unit of force, not energy. Pascal is a unit of pressure, the force per unit area. Since heat problems deal with the amount of energy transferred, joules are the appropriate unit.