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Benjamin Franklin identified lightning with electricity when he discovered that lightning conducted, or flowed, through a metal key could be used to charge a jar, thus proving that lightning was an electric discharge and current. Franklin explained that static electricity as a single fluid that could appear both positive and negative. When a substance contained a greater than normal quantity of electric fluid, it possessed one kind of electric charge; when it contained a less than normal quantity, it possessed the other kind.

Franklin was also the first person to estimate the size of atom. Franklin observed that a teaspoon full of oil would cover the surface of an entire body of water covering half an acre at a pond at Clapham. Franklin measured the ripples off the water surface.

Robert Millikan also had an oil drop experiment, though his experiment entailed balancing the downward gravitational force with the upward drag and the electric forces on tiny charged droplets of oil between the two metal electrodes. Millikan knew the density of the oil, their masses, therefore the gravitational and buoyant forces as well. He calculated the electric field so he could measure the droplet’s charge.

The charge he calculated on a single electron was 1.592×10−19 C, though at this time, the existence of subatomic particles was not universally accepted just yet. Millikan won the Nobel Prize in Physics because of this experiment.

Charles-Augustin de Coulomb invented a device, dubbed the torsion balance, that allowed him to measure very small charges and experimentally estimate the force of attraction or repulsion between two charged bodies. The data he obtained through his extensive use of the torsion balance enabled Coulomb to formulate one...

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... millivolts.
3. Scale comparison of a proton to an electron:

4. An electric field becomes so intense that the electrons at the earth's surface are repelled into the earth by the strong negative charge at the bottom of the cloud. The repulsion of electrons causes the earth's surface to acquire a strong positive charge. In the process of the water cycle, moisture accumulates in the atmosphere, which form clouds. Interestingly, clouds contain millions of water droplets and ice suspended in the air. As the process of evaporation and condensation continues, these droplets collide with other moisture that is in the process of condensing as it rises.The importance of the collisions is that electrons are “knocked off” of the rising moisture, thus creating a charge separation. The newly “knocked-off” electrons gather at the bottom of the cloud, giving it a negative charge.

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