|MadSci Network: Physics|
The value for the charge of an electron was determined using the so called Millikan Oil Drop experiment. Very basically charged droplets of oil are suspended in an electric field. The electric field is known and the weight of the droplet is calculated. Now the force (which equals the weight) suspending the droplets is due to the field (known) and the charge (unknown) on the droplets. So the charge on that droplet can be determined. The charge is made up of "free" electrons on the oil droplet. The experimented is repeated many many times. Eventually a discrete integer value can be determined that is a factor of all the various different charges the oil droplets had, and of the difference in charge the droplets had. The charge, and the difference in charge, must be an integer number of electrons. This number is thus the charge of a single electron. Read more on it here http://www.physchem.co.za/Static%20Electricity/Millikan.htm http://en.wikipedia.org/wiki/Oil-drop_experiment Martin Smith
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