# Energy Resources and Transfer: Energy Transfers

## Energy Resources and Transfer: Energy Transfers

• Energy transfers can occur in many ways, such as by heating, radiation, electrical work or by force.
• These transfers can occur between different energy stores, such as thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear, and internal energy.
• Energy cannot be created or destroyed, only transferred or transformed. This is known as the principle of conservation of energy.
• When energy is transferred, some usually becomes wasted energy - resulting in a less efficient energy transfer.
• Work is done whenever force causes a displacement. Work done on an object is equal to the force applied times the distance moved by the object.
• The rate at which work is done or energy is transferred is called power. The unit of power is the watt (W), equivalent to one joule per second.
• Energy efficiency can be calculated using the formula: efficiency = efficient power transfer/total power input. Efficiency is usually represented as a decimal or a percentage.
• When an energy transfer involves a heating process, the amount of energy transferred can be calculated using the formula: energy transferred = mass x specific heat capacity x change in temperature.
• In a closed system, no energy or matter is transferred in or out, the total energy remains constant.
• Conduction, convection and radiation are three modes of energy transfer. Conduction occurs through solids, convection through fluids, and radiation through any kind of matter, including vacuum.
• Insulation can limit energy transfers by all three methods, reducing energy waste and improving efficiency.
• Sankey diagrams are a useful tool to visually represent energy transfers, showing the useful energy outputs, wasted energy and total inputs.
• Although energy transfers are usually represented as linear sequences, they often occur in complex interrelated systems, where many transfers can occur simultaneously and affect one another.