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Also in Hydrogen explained Hydrogen Production of hydrogen Use of hydrogen. Everything is made of atoms To understand electricity, some basic information about atoms is helpful. Note that the electric field of a neutral atom is weak, but is not exactly zero because the atom is not a point particle. If another atom gets close enough to the atom, they may begin to share electrons. Chemically, we say that the atoms have formed bonds. In contrast to neutral atoms, the field due to an ionized atom is strong, even at larger distances.
The strong electric field of ions makes them strongly attracted to other atoms and molecules, to the point of being highly chemically reactive. Ionized atoms can be free radicals, which are atoms with a dangling bond that are highly reactive. In the human body, free radicals can react with DNA, leading to mutations and possibly cancer. Atoms become ionized when light with enough energy knocks off some of their electrons. Only light waves at the frequencies of X-rays and gamma rays have enough energy to ionize atoms and therefore lead to cancer.
The cancer-causing power of only certain frequencies is why you can use your cell phone as much as you want, but you can only get an X-ray image taken on rare occasions. Free radicals occur naturally in your body. This is more subtle and more difficult to explain in words alone. See Figure Here we see positive charge on the rod pulling negative charge to the nearby metal surface of the electroscope leaving positive charge on the two leafs. Note that the total charge on the electroscope is zero.
What has happened is that the charge gets rearranged as a result of the rod being placed nearby. This suggests that the charge on the rod affects the nearby environment so that charge in the electroscope "feels" its presence.
What happens is that an electric field is created by the charge on the rod. This electric field influences the distribution of charge on the electroscope. We made sparks fly across a gap between two metal spheres. Electrons were transferred by a rotating belt on to one of the spheres. As described above, the charges create an electric field which spans the space between the two spheres. The electrons jump the gap and settle on the other sphere which is grounded.
Grounding has to do with establishing an electrical connection to the earth which has the effect of neutralizing the electrical charge on an object. The flow of electrons between spheres results in the spark we see. But do we actually see the electrons? No, what we see results from the electrons striking atoms in the air between the spheres. The struck atoms become "excited" and when the atoms jump back to a deexcited state they emit light.
That is what we see as the spark. We are able to attract a metal can or even a large delicately balanced wood plank with charges on a rubber rod. We explain this by noting, as we explained the electroscope, that the presence of charge creates an electric field.
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