Conservation of Energy

The Principle of Conservation of Energy

• The law of conservation of energy states that energy cannot be created or destroyed, but only changed from one form into another.

• This implies that the total quantity of energy in an isolated system remains constant, which is also referred to as energy is conserved.

• The overall amount of energy remains constant in a closed or isolated system. This means that in any system closed to transfers of matter and energy, the mass-energy of the system must remain constant over time as the system’s energy or matter cannot be converted to energy or matter outside the system.

Types of Energy

• Different forms of energy include kinetic, potential, thermal, chemical, nuclear, electrical, magnetic, sound and light energy, amongst others.

• Kinetic energy is associated with the motion of an object.

• Potential energy relates to the position or state of an object. This includes gravitational potential (energy due to height) and elastic potential energy (energy stored by stretching).

• Thermal energy is generated from the movement of particles within an object, while chemical energy is stored in chemical bonds, and nuclear energy is stored in the nuclei of atoms.

• Electrical energy is caused by the movement of charged particles (electrons), magnetic energy is due to the alignment of magnetic domains in a material and sound energy is a result of a vibrating object.

• Light energy or radiant energy is the energy of electromagnetic waves.

Energy Transfers

• Energy transfers occur when energy changes from one form to another.

• These transformations between different types of energy can happen in machines and everyday appliances. For example, a torch converts chemical energy from the battery into light and thermal energy.

• In an energy transfer, the amount of energy before the transformation is always equal to the energy after the transformation due to the conservation of energy.

• Any energy transfer is likely to result in some energy being unwillingly transferred to thermal energy, often referred to as ‘wasted energy’.

• Efficiency of an energy transfer is a way of expressing how much of the input energy is usefully transferred or transformed. The greater the proportion of the input energy that is usefully transferred, the more efficient the device.

Sankey Diagrams

• Sankey diagrams are used to represent energy transfers. They show the total energy, the useful energy out, and the ‘wasted’ energy.

• The width of each block represents the proportion of energy in that form. The wider the block, the more energy it represents.

• According to the conservation of energy, the width of the input block in a Sankey diagram (total energy in) will be the same as the total widths of the output blocks combined (useful energy out + ‘wasted’ energy out).

I hope you find these bullet points useful. Should you need further clarifications, I am always here to help.