Fundamentals of Energy: Forms, Transfer, and Measurement

Energy Definition

It is a property of any body or material system which can be transformed by changing its position or state, as well as act on them, originating from other processes of transformation.

Forms of Energy

• Kinetic Energy: Energy possessed by a moving body.
• Potential Energy: Associated with the position of a body relative to a reference point (e.g., the floor).
• Thermal Energy: Due to the vibratory motion of the molecules that constitute matter.
• Radiant Energy: Associated with electromagnetic radiation (such as light or microwaves).
• Nuclear Energy: Associated with the process of fusion (union of nuclei) or fission (rupture of nuclei) that takes place inside atoms.
• Chemical Energy: Associated with chemical reactions (e.g., combustion). This energy is stored in the bonds that hold the atoms and molecules of a substance.
• Electrical Energy: Linked to electric charges in motion.

Properties of Energy

1. The total energy of an isolated system is conserved.
2. Energy can be transmitted (transferred) from bodies or material systems to others.
3. Energy can be transformed from one form to another.

Energy Transfer: Work and Heat

Energy can be transferred between systems. This transfer occurs through interactions between bodies or systems, resulting in changes and transformations.

Work

The mathematical expression that defines work is: T = F × d

The unit is the Joule (J), which is the work done by a force of 1 N (Newton) when the body on which it applies moves 1 m.

Heat

Between bodies or systems that are at different temperatures, the energy transfer that occurs is called heat. Heat is energy in transit.

While the Joule (J) is the standard unit, the calorie (cal) is often used, defined as the amount of heat required to raise the temperature of 1 gram of pure water. The conversion is: 1 cal = 4.186 J.

Units of Energy

Energy is often expressed in terms of power and time. Expressed mathematically as:

ENERGY = POWER × TIME

Other common units are watt-seconds (Ws) or kilowatt-hours (kWh).

Power Definition and Units

The power of a system is the work done in unit time. Its unit in the International System (SI) is the watt (W), defined as the power of a machine that does the work of 1 Joule in 1 second.

• 1 Megawatt (MW) = 10⁶ watts (W) = 10³ kilowatts (kW)
• 1 Gigawatt (GW) = 10⁹ watts (W) = 10⁶ kilowatts (kW)
• 1 Terawatt (TW) = 10¹² watts (W) = 10⁹ kilowatts (kW)