Electricity is a physical phenomenon produced by static or moving electric charges.
In real life, the mechanism of electricity gives many well-known effects, such as lightning, triboelectricity, electrostatic induction, electromagnetic induction, and so on.
Several concepts about electricity
Electron: In an atom, the negatively charged surrounding the nucleus is called an electron.
Electric charge: It is the amount of electronic load, the source of electric field. When a positive charge undergoes a net movement, it constitutes a current in the direction of its movement.
Electric field: The area around the positive or negative charge that generates electricity. The direction of the electric field changes from high potential to low potential.
Voltage: It is a kind of potential energy that tends to make electrons flow through the wire. If you must work on the electric field to move the charge from one point to another, it is said that there is a voltage (potential difference) between the two points.
Electric current: The directional movement of electric charge forms an electric current, usually measured in ampere (Ampere). Any charged particle in motion can form an electric current.
The origin of electricity
In 1767: Joseph Priestley did an experiment and found that in the inside of a charged metal container, the electric force is zero. From the results of this experiment, he accurately guessed that the attraction and gravitation of charged objects acting on each other obey the same law. In 1785, Charles Coulomb used a torsion balance to test Priestley’s conjecture that the force exerted by two charged objects on each other is inversely proportional to the square of the distance. He laid down the basic law of static electricity, namely Coulomb’s law. At this point, the study of electricity has become a kind of precision science.
In 1820: Hans Oster unexpectedly discovered during an experiment in class that the current can deflect the direction of the compass, demonstrating that a magnetic field is generated around the current, which is the Galvanomagnetic effect.
In 1820： Andre Marie Ampere gave a quantitative description of the Galvanomagnetic effect and gave the Ampere’s law and Ampere’s law. The research results of the two of them successfully connected the electric and magnetic phenomena together, collectively called the “electromagnetic phenomenon.”
In 1831: Michael Faraday and Joseph Henry independently discovered electromagnetic induction-changes in magnetic fields can generate electric fields.
In 1865: James Maxwell integrated electromagnetism, proposed Maxwell’s equations, and deduced the electromagnetic wave equation.
In the nineteenth and twentieth centuries, electricity developed vigorously. So far, the theoretical system of electromagnetics tends to be perfected.
In 1859: The German physicist Julius Plück applied a high voltage between the electrodes at both ends of the vacuum tube to make a cathode ray.
In 1897: Joseph Thomson did experiments to prove that the cathode rays are composed of negatively charged particles called electrons, so he discovered electrons.
In 1905: Albert Einstein published a paper explaining many experimental data of the photoelectric effect. Einstein argued that the light beam is composed of a group of discrete quanta (now called photons), rather than continuous fluctuations. If the frequency of the photon is greater than a certain limit frequency, the photon has enough energy to make the electrons on the metal surface escape, causing the photoelectric effect.
Alternating current refers to the current whose current direction changes periodically with time, and the average current in one cycle is zero. Unlike direct current, its direction changes over time, while direct current does not change periodically. Usually alternating current (AC for short) has a sinusoidal waveform. Alternating current can effectively transmit power. But in fact, there are other waveforms, such as triangular waves and square waves. The mains electricity used in daily life is an alternating current with a sinusoidal waveform.
Direct current (DC)
Direct current is an electric charge, usually electrons, flowing in one direction. The current density changes with time, but the direction of movement is usually the same at all times. As an adjective, DC can be used as a reference voltage (its polarity will never change).
In a DC circuit, electrons are formed from the cathode, negative electrode, and negative magnetic pole, and move to the anode, positive electrode, and positive magnetic pole.
Direct current can be generated by electrochemistry, photovoltaic cells or battery packs, or by rectification of alternating current. Alternating current can be converted to direct current through a power supply consisting of a converter, a rectifier (to prevent the current from flowing in the opposite direction), and a filter (to eliminate the jitter in the current flowing out of the rectifier).
Virtually all electronic and computer hardware require direct current to work. The demand for current ranges from close to zero in electronic watches to over 100 amperes required by wireless communication energy amplifiers. Devices that use vacuum tubes, such as high-energy radio or television broadcast transmitters or cathode ray tube (CRT) displays, require about 150 volts to several thousand volts of direct current.
You can read What is the difference between AC and DC here.
American scientist Thomas Alva Edison successfully trial-produced the light bulb on October 21, 1879. This is a milestone in the use of electricity by mankind.
Today, electricity has become a modern necessity. Whether in life or in industry, you can always find it.
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