Energy Transfers

Energy transfers describe how energy is moved from one place to another, or how it changes from one form to another.

Types of Energy

Energy can exist in various forms such as kinetic, thermal, chemical, gravitational potential, elastic potential, nuclear, electrostatic and magnetic energy.
All these types of energy can be grouped into two main categories: potential energy (stored energy) and kinetic energy (the energy of motion).

Central to understanding energy transfers is the principle of energy conservation, which states that energy cannot be created or destroyed, only transferred or transformed from one form to another.
An energy transfer occurs when energy moves from one object/substance to another, or from one form to another. For example, a light bulb transforms electrical energy into light and thermal (heat) energy.
An energy transformation takes place within the same object or system. For example, potential energy of a skier at the top of a hill transforms to kinetic energy as they ski down the slope.

There are often energy losses in transfers, often as waste heat. This can reduce the efficiency of the system.
The efficiency of an energy transfer or transformation can be calculated using the formula: Efficiency = (useful energy output / total energy input) x 100 %
Devices or systems that reduce energy losses, and therefore increase efficiency, are important for sustainable development and energy conservation.

In homes, energy is often transferred from the mains electrical supply into useful forms like light, heat, kinetic or sound energy.
Some common examples of energy transfers in homes include: a kettle transforming electrical energy into heat energy, a stereo transforming electrical energy into sound energy, and a television transforming electrical energy into light, sound and heat energy.

The energy transfers in our homes and industries often rely on either non-renewable energy sources (such as coal, oil and natural gas) or renewable energy sources (such as wind, solar, hydro-electric and geothermal energy).
The growing awareness of climate change drives the transition from non-renewable to renewable energy sources and the need for more efficient energy transfer systems.

Energy transfers are also found in biological systems. For example, in a food chain, energy is transferred from one organism to another when one is eaten by the other.
Much of the original energy input from the sun, however, is lost at each trophic level in a food chain, often as heat.