Electric Batteries
The principle of battery and their types. Learn more on how electricity is stored or produced by different batteries.
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A small current is generated when light falls on certain metals, such as selenium. This is the basis of the cells which power spacecraft. Photographic light meters work on the same principle.
Very hot gases will conduct electricity and a current of electricity will be produced in them if they are made to cut magnetic lines of force. This current can be picked up by metal electrodes. This is called magnetohydro-dynamics (MHD) and is a possible method of producing electricity in the future.
Other ways to generate electricity
There are a number of other ways of producing an electric current. A very small current is produced, for instance, when the junction between two different metals is heated. This device is called a thermocouple. Another method is given the name magnetohydrodynamics (MHD). This is simply a way of converting heat energy to electrical energy at high temperatures and employs no moving parts. It is based upon the fact that gases at high temperatures can conduct electricity. Whenever a conductor cuts across a magnetic field a current is generated in that conductor no matter whether it is a metal, a liquid or a gas. Consequently, if the hot gas from burning fuel is swept between the poles of a magnet a current is generated in it which can be picked up by pieces of metal (electrodes) within the tube.
The familiar static electricity effects occur when an object such as a comb or a pith ball is given an excess of electrons, or if a number of them are removed. It then becomes either negatively or positively charged. Positively and negatively charged pieces of material will attract each other. Two positively or two negatively charged objects will repel each other. On a much larger scale, clouds charged with static electricity lose their charge by means of an electric spark which we call lightning.
