Conservation of energy Study Guide

Energy sources on Earth are broadly categorised into renewable and non-renewable. Non-renewable sources, such as fossil fuels (coal, oil, natural gas) and nuclear fuels (uranium), are finite and cannot be replenished on a human timescale. They are typically used for large-scale, continuous power generation due to their high energy density and reliability, but their use can lead to environmental issues like greenhouse gas emissions or radioactive waste. Renewable sources, including solar, wind, hydro-electricity, and tidal power, are naturally replenished and considered sustainable. These sources are harnessed using various technologies, like solar panels for the Sun's energy, wind turbines for wind, hydroelectric dams for moving water, and tidal barrages for ocean tides. Bio-fuels, derived from recently living organisms, are also renewable, but their land use can be controversial. The choice and integration of these sources depend on factors like cost, environmental impact, geographical location, and desired scale of energy production.

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.