Energy - Transfer of Energy 02

One of the most readily available and easiest to use sources of energy is electricity, without it, life would be very different. The discovery of the first source of useful electrical energy is credited to Alessandro Volta, an Italian scientist. He built the world's first battery made from alternating copper and zinc discs separated by brine soaked card. Before this, only static electricity was known. Or was it? Archaeologists have discovered pots with sheets of copper inside at Roman and Persian sites - they believe these may have been used as batteries but no-one knows for sure.

About thirty years after Volta made his battery, Michael Faraday discovered electromagnetic induction. He found that moving a magnet next to a wire (and vice-versa) created a potential difference (voltage) across the ends of the wire. Over the next few decades, this discovery was developed to make the first mechanical generators of electrical energy. Engineers designed bigger and better generators and not long after the First World War, an early form of the National Grid had been established.

Initially, the use of electricity in the home was limited to lighting but gradually, other useful household devices were invented to take advantage of the availability of electricity. In industry, powerful electromagnets and electric motors were designed, replacing machinery that was once driven by wind, water or steam.

Many electrical appliances convert electricity into more than one type of energy. Some of these energies are produced deliberately and are useful. The non-useful forms are called waste energy and are transferred to the surroundings, often in the form of heat. The ultimate fate of all energy is that it will end up being spread out very thinly throughout the entire universe. You need to be able to recognise the main energy changes in household appliances and be able to recognise which are useful and which are waste.

The amount of transferred useful energy compared with the amount of wasted energy is known as the efficiency. Efficiency is expressed as a percentage. Some electrical devices are extremely efficient e.g. transformers but others are not e.g. a filament light bulb transfers only about ten percent of the original electrical energy into light energy. Energy transfer efficiency is often represented using a Sankey diagram.

One of the major disadvantages of generating electrical energy is that a large percentage of it is obtained from the chemical energy that is contained in fossil fuels. This is released as heat energy by burning. The burning of fossil fuels releases carbon dioxide and other pollutants into the atmosphere. Most scientists believe that the increase in global warming that has been seen happening since the 1940s is due to the increase in the use of fossil fuels as a source of energy. Scientists and engineers are now finding more ways of obtaining electrical energy from sources that don't involve the burning of fossil fuels.