The Electron
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| The Electron | |
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| Subject: | Physics |
| Paper | 1 |
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| Level | H&O |
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Introduction
The concept that there was a natural unit of electricity in each atom was suggested by George Stoney in 1891. He coined the term the 'electron'. In 1895, J.B. Perrin showed that cathode rays have a negative electric charge. In 1897 J.J. Thomson found that electrons are deflected by a magnetic field in a way which shows they are a beam of a negative charge. He also deflected electrons using an electric field. The electron beam was deflected by a fixed amount by a magnetic field (and also by an electric field), meaning that all electrons have the same mass and electric charge.
Electrons have a negative charge
Experiments show us that electron(/cathode rays):
1. Travel in straight lines
2. Cause fluorescence
3. Affect photographic plates
4. Cause a heating effect when they strike a small target
5. Can pass through thin metal foil
6. Are deflected by magnetic and electric fields in a direction that illustrates their negativity
7. Produce X-Rays when the strike a heavy metal target
8. Have a nature independent of the metal used in the cathode
Energy of an electron
An electron accelerated across a potential difference of 1 volt has an energy of one electron-volt or 1 eV. When the voltage is 5,000 V the energy is said to be 5keV
