The fee of the electron is equivalent to the size of the elementary fee (e) but bearing a an adverse sign. Since the worth of the elementary fee is approximately 1.602 x 10-19 coulombs (C), then the fee of the electron is -1.602 x 10-19 C.
When expressed in atom units, the elementary charge takes the worth of unity; i.e., e = 1. Thus, the electron’s charge can be denoted by -e. Return the proton is much an ext massive than the electron, that only has a charge of e. Hence, neutral atoms constantly bear the same variety of protons and also electrons.
JJ Thomson is the undisputed discoverer that the electron. However, despite all those experiments he performed on it, he can only regulate to obtain the electron’s fee to massive ratio. The distinction of being the very first to measure up the electron’s fee goes come Robert Millikan through his oil-drop experiment in 1909.
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The Millikan Oil-Drop Experiment
Here’s the simple idea. If you recognize the density and dimensions (thus consequently the volume) of a substance, it’s going to be easy to calculation its mass and the pressure that gravity exerts ~ above it, a.k.a. Weight. If friend recall, load is simply m x g.
Now let’s assume these substances to be charged oil drops. If you subject these autumn to heaviness alone, they’ll loss freely. However, if they are enabled to autumn in a uniform electric field, your trajectory will be transformed depending on the direction and magnitude that the field.
If the forces as result of the field are command opposite to gravity, the bottom velocity that the particles might decrease. At some point, when the upward force is same to the downward force, the velocities may even go down to zero and the particles will remain in mid-air.
At this specific instance, if we know the size of the electric field (in N/C, units defining the force per unit charge) and the weight of each particle, we can calculate the pressure of the electrical field top top a single particle and finally have the charge.
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Thus, a an easy Millikan Oil-Drop Experiment setup will include an enclosure comprise falling fee oil drops, a an equipment to measure their radii, an flexible uniform electrical field, and also a meter to recognize the field’s magnitude.
By repeating the experiment ~ above a big number that oil drops, Millikan and also his colleague, Harvey Fletcher, derived electron charge values within 1% the the at this time accepted one.
We have some write-ups in Universe now that are regarded the fee of the electron. Here are 2 of them:
Physics World likewise has part more:
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Sources:WikipediaGSU HyperphysicsUniversity of Alaska-Fairbanks
CategoriesAstronomy, overview to space Tagscharge, electric field, electron, elementary school charge, Millikan oil drop, proton