There are two types of energy: Potential energy (stored energy) and kinetic energy (moving energy). All forms of energy are stored in different ways in the energy sources that we use every day. These sources are divided into two groups, renewable energy and non-renewable energy. Renewable and non-renewable energy can be converted into secondary energy sources like electricity and hydrogen. Secondary sources of energy are used to store, move, and deliver energy in easily usable form. We have to use another energy source to make electricity or hydrogen, e.g. coals.

Energy is measured in joules (J). The work done, or energy used, during a certain time is called power. Power is measured in watts (W). A watt is the use of one joule of energy for one second. A watt is a small amount of energy, thus we measure power in units of 1000 watts for one hour, kilowatts for one hour. 

Emotional robots: Will we love them or hate them? - Software that can tell our emotional state is on the way, but will we like machines that can sense how we feel?

Revealed: How pandemic swine flu kills - Two independent studies show that the pandemic H1N1 flu virus binds deeper into the lungs than ordinary flu, which could explain why it is sometimes fatal

GM rice makes allergies easy to stomach - Rice that has been genetically modified to produce pollen proteins and then release them in the gut during digestion is ready for human trials, say its creators

Meadows of the sea in 'shocking' decline - Seagrass meadows, an important habitat for shrimps, crabs and juvenile fish, are disappearing fast