Energy, work, and power
Energy
Energy is always conserved. It is never created or destroyed. Rather, energy is transferred or transformed from one form to another. The main types of energies that you need to know are listed below.
| Gravitational Potential | The energy gained as an object is moved far away from the earth |
| Kinetic | The energy of an object due to its movement |
| Chemical | Stored energy which can be released via a chemical reaction |
| Strain | The energy stored when an object changes shape |
| Electric | Energy carried by an electric current |
| Sound | Energy carried by a sound wave |
| Internal Energy | Total kinetic and potential energies of all particles in an object |
| Thermal (Heat) Energy | Energy released when the temperature of a hot object decreases due to a reduction in its internal energy |
| Nuclear | Stored energy which can be released in a nuclear reaction |
| Light | Energy given off in the form of electromagnetic radiation |
Conservation of Energy
As mentioned above, energy is never created or destroyed – it is only transferred or transformed from one form to another. Here are some common simple examples:
- In a light bulb, electrical energy is transformed into heat energy and light energy
- In a water fall, gravitational energy is transformed into kinetic energy
- In a battery, chemical energy is transformed into electrical energy
The higher an object is from the earth, the greater it’s gravitational potential energy. In the waterfall example above, as the water falls from a higher area to a lower area, the gravitational energy decreases while the kinetic energy increases via the transformation of energy.
Kinetic Energy & Gravitation Potential Energy
Kinetic energy – The kinetic energy of a moving object can be calculated by the formula below:
KE = 0.5 x mv2
Gravitational potential energy – The gravitational potential energy of an object above ground level can be calculated by the formula below:
GPE =mgΔh
[m = Mass(kg), g = Gravitational Force (10 m/s2), Δh = Change in Height(m)
Energy Resources
Energy resources are used to produce electrical energy from other forms of energy
| Fuel | Chemical energy in the fuel is released by burning. The chemical energy can then be transformed into heat energy which turns water into steam. The steam turns turbines which transform the heat into kinetic energy in the generator. Chemical Energy → Heat Energy → Kinetic Energy |
| Waves; Tides; Hydro-electric dams | The gravitational potential energy of falling water is transformed into kinetic energy which passes through turbines to produce electrical energy via the generator. Gravitational Potential Energy → Kinetic Energy → Electric Energy |
| Geothermal Power Stations | Water is pumped underground and gains heat energy from the hot rocks beneath. The heat energy is then converted into kinetic energy in turbines which is used to produce electric energy via the generator. Heat Energy → Kinetic Energy → Electric Energy |
| Nuclear Fission | The nuclear energy stored in Uranium-235 is released via nuclear fission. The nuclear energy transforms into heat energy which is used to turn water into steam. The steam turns turbines and its kinetic energy becomes electrical energy in the generator. Nuclear Energy → Heat Energy → Kinetic Energy → Electrical Energy |
| Solar Power Station | The heat energy from the sun is concentrated via mirrors which focus the heat. The heat energy is used to turn water into steam. The steam turns turbines and its kinetic energy becomes electrical energy in the generator. Heat Energy → Kinetic Energy → Electrical Energy |
| Solar Cells | Light energy from the sun can be transformed into electrical energy. Light Energy → Electrical Energy |
Efficiency
DIAGRAMMATIC REPRESENTATIONS OF ENERGY TRANSFER:
Sankey diagrams are used to show the different forms of energy emitted from a single energy input. For this course you will only need to know how to interpret these diagrams.
This basically shows the input energy and how much of that energy is converted into what in a visual form of arrows that split off. The arrow heads usually add up to the other end of the arrow to represent conservation of energy