Electric charge: what it is and how it is measured

In nature, not everything can be explained from the point of view of mechanics, MKT and thermodynamics, there are also electromagnetic phenomena that affect the body, while not depending on their mass. The ability of bodies to be a source of electromagnetic fields is characterized by a physical scalar quantity - an electric charge. It was first introduced in Coulomb's law in 1785, but attention was drawn to its existence even before our era. In this article, we will tell you in simple words what an electric charge is and how it is measured.

History of discoveries

Even in antiquity, it was noticed that if you rub amber on silk, the stone will begin to attract light objects to itself. William Hilbert studied these experiments until the end of the 16th century. In the report on the work done, objects that can attract other bodies are called electrified.

The next discoveries in 1729 were made by Charles Dufay, observing the behavior of bodies when they rub against different matter. Thus, he proved the existence of two types of charges: the first are formed when resin rubbing against wool, and the second when glass rubbing silk. Logically, he called them "resinous" and "glassy". Benjamin Franklin also explored this issue and introduced the concepts of positive and negative charge. In the illustration - B. Franklin catches lightning.

Charles Coulomb, whose portrait is shown below, discovered the law, which was later called Coulomb's law. He described the interaction of two point charges. He was also able to measure the value and invented a torsion balance for this, which we will talk about later.

And already at the beginning of the last century, Robert Milliken, as a result of the experiments, proved their discreteness. This means that the charge of each body is equal to an integer multiple of the elementary electric charge, and the electron is elementary.

Theoretical information

An electric charge is the ability of bodies to create an electromagnetic field. In physics, the section of electrostatics studies the interactions of charges that are stationary relative to the selected inertial frame of reference.

What is measured

The SI unit of measurement is called "Coulomb" - it is an electric charge passing through a conductor cross-section of 1 Ampere in 1 second.

The letter designation is Q or q. It can take both positive and negative values. The name is in honor of the physicist Charles Coulomb, he derived a formula for finding the forces of interaction between them, it is called "Coulomb's Law":

In it, q1, q2 are the moduli of charges, r is the distance between them, k is the proportionality coefficient.

The formula is similar to the law of attraction, in principle, it describes such an interaction. It has the smallest mass. Its electric charge is negative and it is equal to:

-1.6 * 10 ^ (- 19) Cl

A positron is the opposite of an electron and also consists of one positive elementary charge.

In addition to being discrete, quantized, or measured in portions, the Law of Conservation is also valid for it charges, which suggests that in a closed system only charges of both signs. In simple language - the algebraic (taking into account signs) sum of the charges of particles and bodies, in a closed (isolated) system always remains unchanged. It does not change with time or when the particle moves, it is constant during its lifetime. The simplest charged particles are conventionally compared with electric charges.

The law of conservation of electric charges was first confirmed by Michael Faraday in 1843. This is one of the fundamental laws of physics.

Conductors, semiconductors and dielectrics

There are many free charges in conductors. They move freely throughout the body. There are almost no free carriers in semiconductors, but if you transfer a small energy to the body, they are formed, as a result of which the body begins to conduct an electric current, i.e. electric charges start to move. Dielectrics are substances where the number of free carriers is minimal, so the current cannot flow through them or can under certain conditions, for example, a very high voltage.

How the interaction is expressed

Electric charges attract and repel each other. This is similar to the interaction of magnets. Everyone knows that if you rub a ruler or ballpoint pen on your hair, it becomes electrified. If you bring it to paper in this state, it will stick to electrified plastic. During electrification, a redistribution of charges occurs, so that there are more of them on one part of the body, and less on the other.

For the same reason, you are sometimes electrocuted by a wool sweater or other people when you touch them.

Output: electric charges with one sign tend to each other, and with different ones - they are repelled. They flow from one body to another when they touch each other.

Measurement methods

There are a number of ways to measure electrical charge, let's take a look at some of them. The measuring device is called a torsion balance.

Coulomb's balance is a torsion balance of his invention. The meaning lies in the fact that a light rod with two balls at the ends and one stationary charged ball is suspended in a vessel on a quartz thread. The other end of the thread is attached to the cap. The stationary ball is removed in order to impart a charge to it, after which you need to install it back into the vessel. After that, the part suspended on the thread will begin to move. The vessel is marked with a graduated scale. The principle of its operation is reflected in the video.

Another device for measuring electrical charge is the electroscope. It, like the previous ones, is a glass vessel with an electrode on which two metal foil sheets are fixed. The charged body is brought to the upper end of the electrode, along which the charge flows down onto the foil, as a result, both leaves will be charged with the same name and will begin to repel. The amount of charge is determined by how much they deflect.

An electrometer is another measuring instrument. Consists of a metal bar and a rotating arrow. When a charged body touches the electrometer, the charges flow down the rod to the arrow, the arrow deviates and indicates a certain value on the scale.

Finally, we recommend watching another useful video on the topic:

We have considered an important physical quantity. The teachings about it allowed to significantly expand the knowledge about electricity in general. The contribution to science and technology is quite significant, and the field of application of this knowledge is associated with medicine. Air ionizers have a positive effect on the human body: they accelerate the delivery of oxygen from the air to the cells. An example of such a device is the Chizhevsky chandelier. Now you know what electric charge is and how it is measured.

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