Section 4 b) Summary

The nine types of energy important to learn are:

• Electrical energy
• Light 
• Sound
• Kinetic
• Nuclear
• Thermal 
• Gravitational
• Chemical

Different actions transform energy between the different types, for example a light bulb connected to a battery would be 

Chemical Energy > Electrical Energy > Light Energy 

However, devices such as lights are not 100% efficient. If we look at the light energy emitted compared to the input we can see that a generic light bulb is only 10% efficient, most energy is wasted as heat. 

But if we look at another Sankey diagram, of a more efficient light bulb designed to save energy, only 25% is wasted as heat, it is 75% efficient:

Conduction

Conduction is heat transfer between particles. It occurs mostly in solids, because the particles are more tightly packed than in liquids or gases. Heat flows from an area of warmth to an area of cool, until it is evenly distributed throughout. Metals are good conductors because of their closely packed ions and free moving electrons. Air is a good insulator because the particles are far away, so it is used to insulate frequently. 

Convection 

Convection is a form of heat transfer that only works in a fluid, because it requires free particles to move and create a convection current. 

Convection is when particles are heated, causing them to have more kinetic energy and thus move more and become less dense, causing the hot air to rise. As more hot air rises, it displaces the air that rose before it, forcing the air to move away, and as it does so,  cool, condense, and sink. This is displaced by more sinking air, and forced back to the source of heat, where it will warm and rise again to repeat the cycle. 

An example of convection is a radiator heating a room, as shown in the diagram above. This is also why in a kettle the heating element is at the bottom, it allows convection to occur and heat the water thoroughly. 

Radiation
All objects emit heat through infrared radiation. It doesn't require particles to be transferred, it is transmitted through electromagnetic waves. Radiation and absorption of heat is increased with  bigger temperature difference, or if the object is more matte and black. 

Insulation

In houses, it is important to create insulating layers to limit heat loss through conduction, convection and radiation. 

In people, we have natural mechanisms to insulate heat (goosebumps make hairs stand on end to trap air, but this doesn't do much anymore compared to when humans were hairier), but we use layers of clothing to trap air between which insulates and limits heat loss.