In physics, energy is a quantity that is often understood as the ability of a physical system to produce another physical system.
Change is produced when energy is transferred from one system to another. A system can transfer energy in three ways: physical or thermodynamic work, heat transfer or mass transfer.
All forms of energy in a system are one of two major components: internal energy and external energy. All types of internal energy and external energy can be classified as kinetic energy or potential energy. Kinetic energy is energy that depends on the mass and motion of the system.
If this system is studied as a whole system it is called external kinetic energy. Thermal energy is internal kinetic energy and refers to the motion of each particle of the system (the motion of the molecules, the motion of the atoms, the motion of the electrons, etc.).
Gravitational potential energy is an external potential energy and so is electrostatic potential energy. Elastic energy is an example of internal potential energy.
The Concept of Conservation of Energy
The German physicist Hermann von Helmholtz has proven that all forms of energy are equivalent. Helmholtz suggested that energy can change from one form to another with the same amount of energy.
The nature of this change in the form of energy proves the concept of conservation of energy. Energy only transforms (changes form) from one form of energy to another. This is in accordance with the law of conservation of energy: energy can neither be created nor destroyed, it can only transform.
Energy Measurement
Since energy is defined as the ability to do work on objects, the measurement of energy is not absolute. Only the transition from one state of the system to another can be determined so that the measurement is very relative to the frame of reference used.
Usually, to simplify the measurement, a basic reference point or a zero point is chosen as the basis of reference.
The methods used to measure energy are usually identical to measurements of fundamental concepts in science, such as the measurement of mass, distance, radiation, temperature, time, electric charge, and electric current. This is natural because energy is a function of these fundamental concepts.
The energy measurement results are then expressed in energy units. The standard unit of energy (in SI) is the Joule. Other forms of energy commonly used are calories, kilowatts per hour (kwh = kilowatts per hour) and British thermal units (Btu).
One calorie is equivalent to 4.18 Joules, 1 kWh is equivalent to 3.6 million Joules and one Btu is equivalent to 1055 Joules.
Forms of Energy
The following are forms of energy that are common in the context of physics:
- Thermal Energy (Heat)
- Chemical
- Energy Electrical
- Energy Radiant Energy, energy from electromagnetic radiation.
- Nuclear
- Energy Magnetic
- Energy Elastic
- Energy Sound
- Energy Mechanical
- Energy Light Energy