Some of our clothes are made out of materials that produce electric discharges as we unclothe. Sometimes, the electrical discharge is so powerful that one would can hear faint sounds produced by the electric spark. Basically, the process which takes place as we unclothe is no different by the lightning discharges experienced during a thunderstorm. The electrical discharge is instantaneous in order to balance the electric potential between two points. The energy is released in the form of light and heat, and some lightning discharges can pack so much energy that they practically detonate the air through which it passes, due to instantaneous heating of the air.
The objects around us contain billions of electrically charged particles, however most of them are electrically neutral due to the atomic configuration, which most of the time balances the number of positive electrical charges produced by protons housed inside the nucleus, by an equal negative electrical charges represented by electrons orbiting the nucleus. The balance is broken when electrons are stripped from the atom by an input of additional energy, or when it receives a surplus of electrons.
There are a number of ways through which a material can get electrically charged. One of
them is the method known ever since the ancient times, electrical charging by friction. For example, a piece of plastic rubbed by hair receives electrons from the latter, and thus it becomes negatively charged, while the hair is positively charged.
Electrically charged objects present forces of attraction or repulsion, depending on the sign of the charge held by the interacting objects. Objects presenting charges of the same sign present a force of repulsion towards each other, while differently charged objects attract each other. Most of the materials that get electrically charged by friction are isolators, however some conductors can also present similar behavior.
Nevertheless, an electrically charged conductor will quickly become neutral as it conducts electrical current, thus it has increased electron mobility. Let;s take for example two metal spheres, each electrically charged with different sign charges. If you create a galvanic connection between the two, another electric conductor, a metal wire for example, electrons will flow from the negatively charged sphere towards the positively charged one, thus creating an electrical current through the metal wire, canceling the electric potential between the two spheres.
In the 18th century, multiple scientists experimented with electric generators, such as large machines that were used to generate huge electrical charges. Towards the end of the 18th century, Alessandro Volta created the first electrical cell that could produce a constant electrical current between the electrodes. Anr electric cell represents a device that uses a set of chemical reactions, redox that takes place between the anode, cathode and an electrolyte solution. During the reduction and oxidation process, electrons are collected at the cathode, while the anode receives electrons through an external circuit from the cathode.
One of the most known properties of electric conductors is the electrical resistance. Some of the conductors with the lowest electrical resistance are gold and silver, while copper - a rather inexpensive material - is mostly used in applications, though it has a slightly higher resistance. Electrical resistance represents the measured resistance of a conductor, one meter long, as a voltage of 1 volt is applied to the ends of the conductor while being crossed by a current with the intensity of 1 ampere.
In 1827, a German scientist by the name of Georg Ohm discovered the relationship between the electric potential, current intensity and electrical resistance, known as Ohm's law. In honor of his discovery, the measuring unit for the electrical resistance currently bears his name.
At the same time, scientists had been studying the strange force experienced between magnetite and regular iron. First discovered in 600 BC, the magnetic force was mostly used to create magnetic compasses, phenomenon discovered in 200 BC by the Chinese, which started to be used in Europe only by the 13th century.
The relationship between the magnetic and the electric force was only discovered in the 1819, when a Danish physics professor Hans Oersted tried to demonstrate that a metal wire would heat up under the action of an electric current. Instead, during the experiment, he found a much more important phenomenon which took place as electrical current was being pumped through the electric wire. The compass in the vicinity of the experiment deviated in a position perpendicular to the metal wire, and regained its initial position after removing the electric current.
He tried to explain the phenomena, but failed. Nevertheless, Michael Faraday demonstrated as a set of four simple equations the relationship between electricity and magnetism, two years after Oersted's discovery. Faraday was also the first to suggest that the light has an electromagnetic nature. Using the newly discovered relation, Faraday set to construct the first electric engine, while the American physicist Joseph Henry demonstrated that electrical current could be generated with the help of magnetism in 1831.