The effects of electric current: thermal, chemical, magnetic, light and mechanical. What is the magnetic effect of current? What is the magnetic effect of electric current?

The presence of current in an electrical circuit is always manifested by some action. For example, working under a specific load or some related phenomenon. Consequently, it is the action of electric current that indicates its presence as such in a particular electrical circuit. That is, if the load is working, then the current takes place.

It is known that electric current causes various kinds of effects. For example, these include thermal, chemical, magnetic, mechanical or light. At the same time, various actions electric current capable of expressing themselves simultaneously. We will tell you in more detail about all the manifestations in this material.

Thermal phenomenon

It is known that the temperature of a conductor increases when current passes through it. Such conductors are various metals or their melts, semimetals or semiconductors, as well as electrolytes and plasma. For example, when an electric current is passed through a nichrome wire, it becomes very hot. This phenomenon is used in heating devices, namely: in electric kettles, boilers, heaters, etc. Electric arc welding has the highest temperature, namely, the heating of the electric arc can reach up to 7,000 degrees Celsius. At this temperature, easy melting of the metal is achieved.

The amount of heat generated directly depends on what voltage was applied to a given section, as well as on the electric current and the time it passes through the circuit.

To calculate the amount of heat generated, either voltage or current is used. In this case, it is necessary to know the resistance indicator in the electrical circuit, since it is this that provokes heating due to current limitation. Also, the amount of heat can be determined using current and voltage.

chemical phenomenon

The chemical effect of electric current is the electrolysis of ions in the electrolyte. During electrolysis, the anode attaches anions to itself, and the cathode – cations.

In other words, during electrolysis, certain substances are released on the electrodes of the current source.

Let's give an example: two electrodes are lowered into an acidic, alkaline or saline solution. Then a current is passed through the electrical circuit, which provokes the creation of a positive charge on one of the electrodes, and a negative charge on the other. The ions that are in solution are deposited on the electrode with a different charge.

The chemical action of electric current is used in industry. Thus, using this phenomenon, water is decomposed into oxygen and hydrogen. In addition, using electrolysis, metals are obtained in their pure form, and also carry out electroplating surfaces.

Magnetic phenomenon

An electric current in a conductor of any state of aggregation creates a magnetic field. In other words, a conductor with electric current is endowed with magnetic properties.

Thus, if you bring a magnetic compass needle closer to a conductor in which an electric current flows, it will begin to rotate and take a perpendicular position to the conductor. If you wind this conductor around an iron core and pass a direct current through it, then this core will take on the properties of an electromagnet.

Nature magnetic field always involves the presence of electric current. Let's explain: moving charges (charged particles) form a magnetic field. In this case, currents of opposite directions repel, and currents of the same direction attract. This interaction is justified by the magnetic and mechanical interaction of magnetic fields of electric currents. It turns out that the magnetic interaction of currents is paramount.

Magnetic action is used in transformers and electromagnets.

Light phenomenon

The simplest example of light action is an incandescent lamp. In this light source, the spiral reaches the required temperature value through the current passing through it to a state of white heat. This is how light is emitted. In a traditional incandescent light bulb, only five percent of all electricity is spent on light, while the remaining lion's share is converted into heat.

More modern analogues, for example, fluorescent lamps, most efficiently convert electricity into light. That is, about twenty percent of all energy lies at the basis of light. The phosphor receives UV radiation coming from a discharge that occurs in mercury vapor or in inert gases.

The most effective implementation of the light action of current occurs in. An electric current passing through a pn junction provokes the recombination of charge carriers with the emission of photons. The best LED light emitters are direct-gap semiconductors. By changing the composition of these semiconductors, it is possible to create LEDs for different light waves (different lengths and ranges). The efficiency of the LED reaches 50 percent.

Mechanical phenomenon

Recall that a magnetic field arises around a conductor carrying electric current. All magnetic actions are converted into movement. Examples include electric motors, magnetic lifting units, relays, etc.

In 1820, Andre Marie Ampère derived the well-known “Ampere’s Law,” which describes the mechanical effect of one electric current on another.

This law states that parallel conductors carrying electric current in the same direction experience attraction to each other, and those in the opposite direction, on the contrary, experience repulsion.

Also, the ampere's law determines the magnitude of the force with which a magnetic field acts on a small segment of a conductor carrying an electric current. It is this force that underlies the functioning of an electric motor.

Electric current in a circuit always manifests itself in some way. This can be either work under a certain load or the accompanying effect of current. Thus, by the effect of current one can judge its presence or absence in a given circuit: if the load is working, there is current. If a typical phenomenon accompanying current is observed, there is current in the circuit, etc.

In general, electric current is capable of causing various effects: thermal, chemical, magnetic (electromagnetic), light or mechanical, and different types of current effects often occur simultaneously. These phenomena and effects of current will be discussed in this article.

Thermal effect of electric current

When direct or alternating electric current passes through a conductor, the conductor heats up. Such heating conductors in different conditions and applications can be: metals, electrolytes, plasma, molten metals, semiconductors, semimetals.

In the simplest case, if, say, an electric current is passed through a nichrome wire, it will heat up. This phenomenon is used in heating devices: in electric kettles, boilers, heaters, electric stoves, etc. In electric arc welding, the temperature of the electric arc generally reaches 7000 ° C, and the metal easily melts - this is also the thermal effect of the current.

The amount of heat released in a section of the circuit depends on the voltage applied to this section, the value of the flowing current and the time it flows ().

Having transformed Ohm's law for a section of a circuit, you can use either voltage or current to calculate the amount of heat, but then you must also know the resistance of the circuit, because it is what limits the current and, in fact, causes heating. Or, knowing the current and voltage in the circuit, you can just as easily find the amount of heat generated.

Chemical action of electric current

Electrolytes containing ions under the influence of direct electric current - this is the chemical effect of current. During electrolysis, negative ions (anions) are attracted to the positive electrode (anode), and positive ions (cations) are attracted to the negative electrode (cathode). That is, the substances contained in the electrolyte are released at the electrodes of the current source during the electrolysis process.

For example, a pair of electrodes is immersed in a solution of a certain acid, alkali or salt, and when an electric current is passed through the circuit, a positive charge is created on one electrode and a negative charge on the other. The ions contained in the solution begin to be deposited on the electrode with the opposite charge.

For example, during the electrolysis of copper sulfate (CuSO4), copper cations Cu2+ with a positive charge move to a negatively charged cathode, where they receive the missing charge and become neutral copper atoms, settling on the surface of the electrode. The hydroxyl group -OH will give up electrons at the anode, resulting in the release of oxygen. Positively charged hydrogen cations H+ and negatively charged anions SO42- will remain in solution.

The chemical action of electric current is used in industry, for example, to decompose water into its constituent parts (hydrogen and oxygen). Electrolysis also makes it possible to obtain some metals in their pure form. Using electrolysis, a thin layer of a certain metal (nickel, chromium) is coated on the surface - this, etc.

In 1832, Michael Faraday established that the mass m of a substance released at the electrode is directly proportional to the electric charge q passing through the electrolyte. If a direct current I is passed through the electrolyte for a time t, then Faraday’s first law of electrolysis is valid:

Here the proportionality coefficient k is called the electrochemical equivalent of the substance. It is numerically equal to the mass of the substance released when a single electric charge passes through the electrolyte, and depends on chemical nature substances.

In the presence of an electric current in any conductor (solid, liquid or gaseous), a magnetic field is observed around the conductor, that is, the conductor carrying the current acquires magnetic properties.

So, if you bring a magnet to a conductor through which current flows, for example, in the form of a magnetic compass needle, then the needle will turn perpendicular to the conductor, and if you wind the conductor around an iron core and pass direct current through the conductor, the core will become an electromagnet.

In 1820, Oersted discovered the magnetic effect of current on a magnetic needle, and Ampere established the quantitative laws of the magnetic interaction of conductors with current.

A magnetic field is always generated by current, that is, by moving electric charges, in particular by charged particles (electrons, ions). Oppositely directed currents repel each other, unidirectional currents attract each other.

Such mechanical interaction occurs due to the interaction of magnetic fields of currents, that is, it is, first of all, magnetic interaction, and only then mechanical. Thus, the magnetic interaction of currents is primary.

In 1831, Faraday established that a changing magnetic field from one circuit generates a current in the other circuit: the emf generated is proportional to the rate of change magnetic flux. It is logical that it is the magnetic action of currents that is used to this day in all transformers, and not just in electromagnets (for example, in industrial ones).

In its simplest form, the luminous effect of electric current can be observed in an incandescent lamp, the spiral of which is heated by the current passing through it to white heat and emits light.

For an incandescent lamp, light energy accounts for about 5% of the supplied electricity, the remaining 95% of which is converted into heat.

Fluorescent lamps more efficiently convert current energy into light - up to 20% of the electricity is converted into visible light thanks to the phosphor, which receives from an electrical discharge in mercury vapor or inert gas kind of neon.

The luminous effect of electric current is realized more efficiently in LEDs. When an electric current is passed through p-n junction in the forward direction, charge carriers - electrons and holes - recombine with the emission of photons (due to the transition of electrons from one energy level to another).

The best light emitters are direct-gap semiconductors (that is, those that allow direct optical band-band transitions), such as GaAs, InP, ZnSe or CdTe. By varying the composition of semiconductors, it is possible to create LEDs for various wavelengths from ultraviolet (GaN) to mid-infrared (PbS). The efficiency of an LED as a light source reaches an average of 50%.

As noted above, each conductor through which electric current flows forms a circle around itself. Magnetic actions are converted into motion, for example, in electric motors, magnetic lifting devices, magnetic valves, relays, etc.

The mechanical action of one current on another is described by Ampere's law. This law was first established by André Marie Ampère in 1820 for direct current. It follows that parallel conductors with electric currents flowing in one direction attract, and in opposite directions they repel.

Ampere's law is also the law that determines the force with which a magnetic field acts on a small segment of a conductor carrying current. The force with which a magnetic field acts on an element of a current-carrying conductor located in a magnetic field is directly proportional to the current in the conductor and vector product element of conductor length for magnetic induction.

It is based on this principle, where the rotor plays the role of a frame with current, oriented in the external magnetic field of the stator with a torque M.

We examined in detail the properties of the electrostatic field generated by stationary electric charges. When electric charges move, a a whole series new physical phenomena that we are beginning to study.

It is now widely known that electric charges have a discrete structure, that is, the charge carriers are elementary particles– electrons, protons, etc. However, in most practically significant cases this discreteness of charges does not manifest itself, therefore the model of a continuous electrically charged medium well describes the phenomena associated with the movement of charged particles, that is, with electric current.

Electric current is the directional movement of charged particles.

You are very familiar with the use of electric current, since electric current is extremely widely used in our lives. It is no secret that our current civilization is mainly based on the production and use of electrical energy. Electrical energy It is enough to simply produce, transmit over long distances, and transform into other required forms.

Let us briefly dwell on the possible manifestations of the action of electric current.

Thermal effect electric current manifests itself in almost all cases of current flow. Due to the presence of electrical resistance, when current flows, heat is released, the amount of which is determined by the Joule-Lenz law, which you should be familiar with. In some cases, the heat released is useful (in a variety of electric heating devices); often the heat release leads to useless energy losses during the transmission of electricity.

Magnetic action current manifests itself in the creation of a magnetic field, leading to the appearance of interaction between electric currents and moving charged particles.

Mechanical action current is used in a variety of electric motors that convert the energy of electric current into mechanical energy.

Chemical action manifests itself in the fact that a flowing electric current can initiate various chemical reactions. For example, the process of producing aluminum and a number of other metals is based on the phenomenon of electrolysis - the decomposition reaction of molten metal oxides under the influence of electric current.

Light action electric current manifests itself in the appearance of light radiation when an electric current passes. In some cases, the glow is a consequence of thermal heating (for example, in incandescent light bulbs); in others, moving charged particles directly cause the appearance of light radiation.

In the very name of the phenomenon (electric current) one can hear echoes of old physical views, when everything electrical properties were attributed to a hypothetical electric fluid filling all bodies. Therefore, when describing the movement of charged particles, terminology is used similar to that used when describing the movement of ordinary liquids. This analogy extends beyond a simple coincidence of terms; many of the laws of motion of electrical fluid are similar to the laws of motion of ordinary fluids, and the partially familiar laws of direct electric current through wires are similar to the laws of motion of fluid through pipes. Therefore, we strongly recommend that you repeat the section that describes these phenomena - hydrodynamics.

1. What is the magnetic effect of electric current? Explain your answer.

The ability of an electric current passing through conductors of the second type to generate a magnetic field around these wires

2. How can you determine the poles of a magnet using a compass? Explain your answer.

The north pole of the arrow is attracted to the south pole of the magnet, the south pole to the north.

3. How can you detect the presence of a magnetic field in space? Explain your answer.

For example, using iron filings. Under the influence of the magnetic field of the current, iron filings are located around the conductor not randomly, but in a concentric circle.

4. How can you use a compass to determine whether current is flowing in a conductor? Explain your answer.

If the compass needle is perpendicular to the wire, then direct current is flowing in the wire.

5. Is it possible to cut a magnet so that one of the resulting magnets only has North Pole, and the other is only southern? Explain your answer.

It is impossible to separate the poles from each other by cutting. Magnetic poles only exist in pairs.

6. How can you find out if there is current in a wire without using an ammeter?

• Using a magnetic needle that responds to current in a wire.
• Using a sensitive voltmeter, connecting it to the ends of the wire.