Conservation of energy Study Guide

In a closed system, energy can be transferred from one store to another, or from one form to another, but the total amount of energy within that system remains constant. For example, when a light bulb is turned on, electrical energy is converted into light and thermal energy. While the forms of energy change, the sum of the light energy and thermal energy produced will exactly equal the electrical energy consumed. This principle, known as the conservation of energy, means that energy can never be created or destroyed, only transformed or moved. Consequently, in a closed system, there is no net change to the overall quantity of energy present, even though its distribution among a system's components or its manifested forms might vary significantly.

The principle of conservation of energy states that energy cannot be created or destroyed. In any system, the total amount of energy remains constant over time. Although energy can be transferred from one store to another, or from one object to another, the total quantity of energy within a closed system is preserved. For instance, in a swinging pendulum, potential energy is converted to kinetic energy and vice versa, but the sum of these energies (assuming no external forces like air resistance) stays the same. Similarly, when a car brakes, its kinetic energy is primarily transferred to thermal energy in the brakes and tires due to friction.