Units 6, 7, and 8: All about Energy (and work done and power)

In this section, we will go over energy stores, energy transfers, and power.

remember, all the formulae you will need is in the formulae page.

According to the first law of thermodynamics, energy cannot be created or destroyed. But it can be transferred between energy stores.

Main types of energy

Kinetic

Gravitational Potential

Chemical

Electric

Thermal

Internal (can be increased by heating)

Elastic potential (in springs)

Transfer of energy between stores can be best illustrated through the pendulum, where the total energy of the system remains constant (assuming no air resistance) , it just switches between GPE (gravitational potential energy) and kinetic energy.

In reality, no systems are 100% efficient at transferring energy.

to calculate percentage efficiency: useful energy/total energy * 100

You might be required to draw a Sankey diagram:

simply draw the thickness of the arrows in proportion to the percentage energy lost/transferred.

The only equations you need to know for IGCSE are the ones for GPE and Kinetic energy, which can be found in the 'formulae' section.

It is important to know where our energy comes from.

The sun provides us with Solar, Wind, and Fossil fuels (sun allows plants to photosynthesise) and all other energy except for geothermal, nuclear, and tidal.

You will have to remember the types of renewable and non-renewable energy.

advantages and disadvantages:

Now, onto work done and power.

Work done is the energy transferred by a force. So it is measured in joules

WD = force * distance

Power is the rate at which energy is transferred, or the rate at which work is done.

Power = Change in energy/time

this energy can also be work done, depending on the question. If you want to more power, increase the energy transferred or decrease the time taken.

That's it for now. It is important to note that I have omitted certain details to make this as concise and helpful as possible. If there is something I have not covered here, please leave a comment on the forums.