What is electric current in simple terms?

Every person has an abstract concept of electric current. For an electrical device, a power source is something like an air source for any breathing organism. But on these comparisons the understanding of the nature of the phenomenon is limited, and only specialists understand the essence more deeply.

Simple words about electric current

The standard definition from a school textbook on physics laconically describes the phenomenon of electric current. But frankly, it can be fully understood if you study the subject much deeper. After all, the information is presented in another language - scientific. It is much easier to understand the nature of a physical phenomenon, if you describe everything in a familiar language that anyone can understand. For example, the current in the metal.

We should start with the fact that everything that we consider to be firm and immobile is only in our view. A piece of metal lying on the ground is a monolithic motionless body in human understanding. For analogy, let's imagine our planet in space, looking at it from the surface of Mars. The earth seems to be a whole, fixed body. If you get closer to its surface, it becomes obvious that this is not a monolithic piece of matter, but a constant movement: water, gases, living beings, lithospheric plates - all this moves non-stop, although this is not visible from far space.

Let's return to our piece of metal lying on the ground. It is motionless, because we look at it from the side as a monolithic object. At the atomic level, it consists of constantly moving smallest elements. They are different, but among all, we are interested in electrons, which create in metals an electromagnetic field that generates the very current. The word “current” must be understood literally, because when elements with an electric charge move, that is, “flow”, from one charged object to another, then “electric current” occurs.

Having dealt with the basic concepts, we can derive a general definition:

An electric current is a stream of charged particles moving from a body with a higher charge to a body with a lower charge.

To more accurately understand the essence, you need to delve into the details and get answers to several basic questions.

Answers to major questions about electrical current

After the formulation of the definition, several logical questions arise.

  1. What makes the current "flow", that is, to move?
  2. If the smallest metal elements are constantly moving, then why is it not deformed?
  3. If something flows from one object to another, does the mass of these objects change?

The answer to the first question is simple. As water flows from a high point to a low one, so electrons will flow from a high charge body to a low body, obeying the laws of physics. A "charge" (or potential) is the number of electrons in the body, and the more of them - the higher the charge. If a contact is made between two bodies with different charges, electrons from a more charged body will flow into a less charged one. So there will be a current that will end when the charges of the two contacting bodies equalize.

To understand why the wire does not change the structure, despite the fact that it is constantly moving, you need to imagine it as a big house in which people live. The size of the house will not change about how many people enter and leave it, as well as move inside. The man in this case is an analogue of an electron in a metal - he moves freely and does not have a special mass in comparison with the whole building.

If electrons move from one body to another - why does the mass of bodies not change? The fact is that the electron's weight is so small that even if all electrons are removed from a body, its mass will not change.

What is the current measurement unit

In order to "calculate" the electric current, different units of measurement are used, we will examine three main ones:

  • Current strength
  • Voltage.
  • Resistance.

If you try to describe the concept of current strength in simple words, it is best to imagine the flow of cars passing through the tunnel. Cars are electrons, and the tunnel is wire. The more cars pass at one time through the cross section of the tunnel - the greater is the current strength, which is measured by the device called "ammeter" in Amperes (A), and in formulas it is indicated by the letter (I).

Voltage is a relative value that expresses the difference in the charges of bodies between which current flows. If one object has a very high charge and the other is very low, then there will be a high voltage between them, for measuring of which a “voltmeter” device is used and a unit called Volt (V). In formulas it is identified by the letter (U).

Resistance characterizes the ability of a conductor, conventionally a copper wire, to pass through a certain amount of current, that is, electrons. The resisting conductor generates heat, expending a portion of the energy of the current passing through it, thereby reducing its strength. Resistance is calculated in Ohms (Ohms), and in formulas use the letter (R).

Formulas for calculating current characteristics

Using three physical quantities, one can calculate the characteristics of the current using Ohm's Law. It is expressed by the formula:

I = U / R

Where I is the current strength, U is the voltage on the circuit section, R is the resistance.

From the formula, we see that the current strength is calculated by dividing the voltage value by the resistance value. From here we have the wording of the law:

The current is directly proportional to the voltage and inversely proportional to the resistance of the conductor.

From this formula, you can mathematically calculate its other components.

Resistance:

R = U / I

Voltage:

U = I * R

It is important to note that the formula is valid only for a specific section of the chain. For a complete, closed circuit, as well as other special cases, there are other Ohm's laws.

Effect of current on different materials and living things

Different chemical elements under the action of current behave differently. Some superconductors do not resist moving electrons through them without causing any chemical reaction. Metals with the excessive stress for them can break down, melt. Dielectrics that do not transmit a current do not enter into any interaction with it at all and thereby protect the environment from it. This phenomenon is successfully used by man in the insulation of wires with rubber.

For living organisms, the current is an ambiguous phenomenon. He is able to have both beneficial and destructive effects. People have long used controlled discharges for therapeutic purposes: from lungs that stimulate brain activity to discharges, to powerful electric shocks that can start a stopped heart and bring a person back to life. A strong discharge can lead to serious health problems, burns, tissue death and even instant death. When working with electrical appliances, you need to follow safety regulations.

In nature, you can find a lot of phenomena in which electricity plays a key role: from deep-sea creatures (electric rays), able to beat with electricity, to lightning during thunderstorms. Man has long mastered this natural power and skillfully uses it, thanks to which all modern electronics work.

It should be remembered that the phenomena of nature can be both beneficial and harmful to humans. Studying at school and continuing education helps people to correctly use the phenomena of the world for the benefit of society.

Watch the video: Electric Current: Crash Course Physics #28 (December 2019).

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