Most likely, you have already experienced such an episode: when you touch something, such as the door handle of your house or car, or when you shake someone’s hand, you feel a shock. Sometimes you can even hear a noise or see a spark.
But, after all, why is this happening?
Professor Claudio Furukawa, in charge of the Demonstration Laboratory at the University of São Paulo’s Institute of Physics (USP), explains that this phenomenon has something to do with static electricity.
Come on: all matter is made of atoms. And atoms, in turn, consist of two main particles: protons (positive) and electrons (negative).
Most of the time, atoms are in a neutral state. In practice, this means that the number of protons and electrons is the same.
But this balance changes when we touch and rub two objects that have different properties.
At that moment, the atoms of both of them come very close, and this can “mix” all those electrons.
The thing may be that the thing is “stealing” some of these particles for itself. That is: a substance has more electrons.
Then the previous state of neutrality ceases to exist. The material that lost electrons becomes positive and the material that gained these particles becomes negative.
This is what happens, for example, when we drag our feet (especially with shoes) on a carpet, or if we wear clothes made of wool and synthetic fabric for some time.
The friction of these different materials (a carpet for feet or a synthetic blouse for arms) causes the electrons to “mix”, electrifying the objects involved in this interaction.
But atoms always seek to return to neutrality. Then, when we touch a third object (which is neutral), like a doorknob, this excess of electrons is literally dumped out.
This generates an electric field that gives us a slight shock (usually followed by fear).
Furukawa describes that “the formation of this electric field is capable of giving off a rapid spark.”
This phenomenon increases in dry days. Low humidity in the air hinders the continuous exchange of molecules, causing the body to accumulate more loads over a period of time.
This is because water molecules are good conductors of electricity and can gradually rid the body of excess electrons.
However, on a dry day, the excess is only discharged once and for all when electrically conductive objects, such as metal surfaces or someone else’s hand, are touched.
It is worth noting that the materials that received that charge (such as a doorknob) are not electrified. The excess particles are distributed over a much larger mass or end up on the floor – because the knob is on the door, which connects to the wall, which connects to the floor, and so on.
make it bad?
Furukawa estimates that for a small spark to jump in the space between the hand and the body, there must be an electric field of 3,000 volts in the area of a millimeter.
The physicist “to compare the two poles of an outlet says there is 110 or 220 volts, which is not enough voltage to spark.”
1.5V battery. “If you put your fingers on both ends of the battery, you won’t get a shock,” says the expert.
But, then, can getting an electric shock when touching things or people be harmful? The answer is no.
According to Furukawa, this is due to two factors: the length of the episode and the location in which it occurs.
“First, the charge of the accumulating particles is relatively low and returns to neutral quickly, in thousandths. Second, the electric field passes through the fingers and does not cross any vital organ, such as the brain or the heart,” he explains.
Although these discharges are harmless, there is no denying that they are a bit annoying. Is there anything that can be done to avoid it?
“The advice is, before touching the place where you usually receive the shock, touch other larger and more versatile objects. In the case of a doorknob, for example, it is helpful to touch the combination of switches that have a larger contact surface,” Furukawa replies.
“You can also turn on a tap and wash your hands or walk barefoot to discharge electrons,” the physicist concludes.
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