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Electricity the BIG Picture
Transcript of Electricity the BIG Picture
William Gilbert (1544-1603)
An English scientist, William Gilbert, coined the term ‘electricity’ and created an instrument called a versorium that could detect static electricity.
He observed that some materials seem to ‘attract’ each other and stick together while others seem to ‘repel’ or push away from each other. This is because some materials, when rubbed, develop a negative charge while others develop a positive charge.
All materials are made from minute particles called atoms. In the middle of each atom is a nucleus of positively-charged protons and around the nucleus are negatively-charged electrons. When we rub a material, the electrons build up a charge and they move to an area of positive charge. This movement of electrons creates electricity.
Benjamin Franklin (1706-1790)
An American scientist, Benjamin Franklin, wanted to prove that lightning was electricity and that it could travel through metal. In 1752, he made a kite with a metal spike on top and he attached a key to the kite string. When he ﬂew his kite in an electrical storm, a bolt of lightning passed down the spike, along the kite string (which had become wet with rain) and into the key, which sparked with electricity.
Luigi Galvani (1737-1798)
Luigi Galvani, an Italian doctor, was dissecting a frog’s leg when he made a remarkable discovery. When he inserted a metal knife into the leg it twitched and appeared to jump into life. He concluded that the muscles in the frog’s leg must contain electricity.
Alessandro Volta, an associate of Galvani, had a different explanation. He believed that electricity will ﬂow from one metal (the steel knife) to a different metal (the tin tray) if you put a wet material (the frog’s leg) between them
The word ‘electricity’ derives from the Greek ‘electron’ meaning amber.
Amber is the sap of trees that lived millions of years ago. The ancient Greeks realised that if you rubbed amber with a cloth, other materials such as feathers and woollen threads would stick to it. We now know that this is because amber becomes charged with static electricity.
The ‘dark’ ages
Electricity powers our modern lifestyle. In our home, work, travel and leisure time most of us are dependent on electricity. It is hard to imagine our lives without it – we would, literally, be stumbling in the dark.
However, we only need to go back 200 years (before the invention of the light bulb) to ﬁnd everyone living without any electricity. They used other things instead, e.g. candles for lighting; wood for heating; horses for transport.
Thunderbolts and lightning
There is one type of electricity that has always been with us: lightning. Long ago, lightning was thought to be a punishment from the gods. People knew lightning was powerful but they didn’t understand where it came from or know how to use it.
We now know that lightning is formed when the movement of air currents causes storm clouds to become charged with static electricity. The negative charge in the clouds builds up until eventually it forms a massive spark – a ﬂash of lightning – that passes through the air. Then we hear thunder – this is a crackle of electricity.
N.B. Do not try this experiment at home – Franklin was lucky to escape with his life!
Franklin coined the term ‘
’ to describe these materials and the spike on his kite gave him the idea for the
Georg Ohm, German physicist, discovered the relationship between voltage, current and resistance – now known as Ohm’s Law. He wrote about his ﬁndings and theory of electricity in a famous book published in 1827.
Alessandro Volta (1745-1827)
Galvani’s discovery gave Volta an idea. He layered alternating discs of copper, cardboard soaked in salty water and zinc so that they formed a stack – now known as a Voltaic pile. Then he attached wires to the top and bottom of the stack and an electric current ﬂowed between them. A modern battery works in a similar way.
The first ever battery!
Alexander von Humboldt (1769-1859)
Galvani was partly right when he thought that the frog’s muscles contained electricity. Humans have electricity in their nerve impulses. We use it to send signals from our brain to other parts of our body.
Electric eels can go even further than this. They can make their own electricity as German naturalist Alexander von Humboldt was to ﬁfind out from his research in 1808. An electric eel’s body contains thousands of electric cells that store electricity like tiny batteries. They can generate a charge of up to 600 volts to stun prey – that’s about ﬁfive times more powerful than an electric socket.
French physicist, Ampère helped discover electro-magnetism. He described a way to measure the ﬂow of electricity. The ampere – a unit for measuring an electric current is named after him.
André-Marie Ampère (1775-1836)
Humphry Davy, English scientist, invented the ﬁrst electric lamp by connecting two wires to a battery then attaching a charcoal strip between the ends of the wires. The charcoal, charged with electricity, glowed with light.
Humphry Davy (1778-1829)
Georg Ohm (1789- 1854)
English physicist and chemist, Faraday studied electricity and magnetism. He wanted to ﬁnd out if they could work together. He discovered that moving a magnet near a coil of copper wire produced an electric current. His research led to the invention of the electric motor and the generator.
Michael Faraday (1791-1867)
An English scientist, Joseph Swan, produced an electric light from a ﬁlament of carbon. To slow down the rate of burning, he designed a glass bulb around the ﬁlament but he couldn’t create a vacuum inside the bulb so the light only glowed for a short time.
American inventor, Thomas Edison, worked out how to create a better vacuum inside
the bulb. He worked with Swan to develop a more long-lasting light bulb. Edison opened electrical power stations in New York and London to carry electricity along wires to street lights. In 1880 the ﬁrst electric street lights were turned on in New York.
Thomas Edison (1847-1931)
Joseph Swan (1828-1914)
Nikola Tesla (1856-1943)
Serbian-American, Tesla discovered how to create an ‘alternating current’ (AC: electricity ﬂowing in alternating directions). This had the advantage over ‘direct current’ (DC: electricity ﬂowing in the same direction) because it could carry electricity over much longer distances without the wires getting too hot and losing power.
Any bright ideas?