Defines Ohm's law. Ohm's law in simple terms. Nonlinear elements and circuits

OMA is the largest chain of construction hypermarkets in Belarus. Today, 24 retail outlets are open in different cities of the country, 4 of which are in the Belarusian capital, where everyone can purchase everything they need for repairs, as well as goods for the home, garden and vegetable garden.

The company was founded in 1992 and over more than 20 years has grown into the most recognizable network of construction hypermarkets in Belarus. Today the company has 24 retail facilities at its disposal: in Minsk, in each of the regional centers, as well as in some large cities of the Republic, for example, in Lida, Baranovichi, Zhlobin, Rogachev and others.

Now the company employs about 3,000 specialists and over 45 thousand people visit OMA construction hypermarkets daily.

Product catalog OMA Minsk

OMA construction hypermarkets in Minsk offer more than 70 thousand items of a wide variety of products: from construction mixtures and power tools to cornices and garden swings.

Here you can find products from famous world brands that have long established themselves in the building materials market as standards of quality: Bosch, Tarkett, Keramin, Condor, Makita, Caparol, PAROC, Ceresit, KNAUF and others. In addition, OMA also produces products of its own brands: some construction dry mixes, paints and varnishes, gardening products, etc.

You can get acquainted with the range of goods of the OMA store in Minsk on the official website of the construction hypermarket. In the catalog section you will find construction tools, building materials, construction equipment, plumbing fixtures, household appliances, household goods, varnishes and paints, workwear, auto products, furniture and much more.

Promotions and discounts at OMA Minsk

OMA construction hypermarkets in Minsk regularly hold promotions. With incredible discounts you can purchase almost any product presented on the shelves of the chain stores. In OMA stores in different cities of Belarus, promotions may differ; in addition, do not forget that promotional products can only be purchased while the product is in stock. If it so happens that the required product is out of stock, it is no longer possible to purchase it at a discount.

You can find out about current promotions and discounts in OMA construction hypermarkets in Minsk in special advertising newspapers. You can find them on the OMA website, in the Promotions section: www.oma.by/sales/

Addresses of stores in Minsk

Today there are 4 OMA stores in Minsk, which are located at the following addresses:

• st. Vaneeva, 38
• st. Napoleon Ordy, 6
• lane Industrial, 12B
• st. D. Martsinkevich, 11

Opening hours Oma Minsk

All OMA stores in Minsk operate on different schedules. For more information about the operating hours of each OMA Minsk store, see below:

st. Vaneeva, 38

• Working hours
  Mon-Sun: from 8:30 to 22:00
  

st. Napoleon Ordy, 6

• Working hours
  Mon-Sun: from 8:00 to 22:00
  Return service: from 09:00 to 21:00

lane Industrial, 12B

• Working hours
  Mon-Sat: from 8:30 to 20:30
  Sun: from 8:30 to 19:00
  Pavilion "Garden and Vegetable Garden":
  Mon-Sat: from 8:30 to 20:30
  Sun: from 8:30 to 19:00

st. D. Martsinkevich, 11

• Working hours
  Mon-Sun: from 8:30 to 20:00

Installment plan

In OMA construction hypermarkets, retail buyers can take advantage of installment plans or loans on favorable terms. Installment plans are offered by several Belarusian banks: VTB Bank, Priorbank, MTBank on the Halva card, Moscow-Minsk Bank on the Smart installment card and Belgazprombank on the purchase card. Everyone's terms and conditions are different, so check them out in advance.

Installment plan with Halva card

All owners of an installment card from MTBank can use the installment plan. The Halva installment plan is valid in all OMA construction hypermarkets in Belarus, as well as in the online store. Installment terms depend on the amount of purchases:

When purchasing goods for a total amount of up to 50 BYN, installments are provided for 2 months;
when purchasing goods for a total amount of 50-200 BYN, the installment period increases to 3 months;
When purchasing goods in the amount of 200-700 BYN, installments are provided for 6 months;
When purchasing goods worth more than 700 BYN, the installment period is 12 months.

Installment plan using a purchase card from Belgazprombank

Installment plan using a Smart card from Moscow-Minsk Bank

The installment terms for the Moscow-Minsk Bank Smart Card also do not depend on the amount of purchases: installments are provided for 2 months. You can use the installment plan using a Smart card in any OMA store in Belarus, as well as in the online store.

Installment plan from VTB Bank

Installment plans in OMA stores on favorable terms can also be obtained from VTB Bank. Installments are available for 3 or 6 months. So, when purchasing goods for a total amount of 50 BYN to 200 BYN, installments are provided for 3 months; when purchasing goods in the amount of 200 BYN to 700 BYN, the installment period increases to six months; and when purchasing goods worth more than 700 BYN, installments are provided for 12 months.

All installment plans are provided without proof of income and a down payment, at 0.1% per annum.

Note!

The installment plan from VTB Bank does not apply to promotional and discounted goods, as well as to goods at special prices. You can also use this installment plan only in some stores of the chain: Minsk (Vaneeva St. 38 and N. Ordy St. 6), Brest, Bobruisk (Minskaya St. 135), Grodno (Gorky St. 91), Zhlobin, Mogilev and Orsha.

Installment plan from Priorbank

Another installment option is provided by Priorbank. You can use this service only if you purchase goods in the amount of 300 BYN to 3200 BYN. In this case, an important condition for the installment plan is an initial payment of 10% of the total amount, as well as registration of insurance for 0.7% of the installment amount.

An installment plan for 3 months is provided subject to the purchase of goods in the amount of 160-200 BYN.
An installment plan for 6 months is provided subject to the purchase of goods in the amount of 200-600 BYN.
An installment plan for 12 months is provided subject to the purchase of goods worth more than 600 BYN.

Note!

The installment plan from Priorbank does not apply to promotional and discounted goods, as well as to goods at special prices. You can use this type of installment plan in all OMA stores.

Discount card

OMA construction hypermarkets offer their customers discount cards that will help them save money. Today, the chain stores have two discount programs: OMA Construction House and New House.

Each discount program has different conditions and amounts of discounts provided. Please read the terms and conditions carefully and choose the most suitable option.

For new residents, OMA construction hypermarkets offer a year of profitable purchases with a 7% discount. Also, under the New Home discount program, you will receive professional advice on choosing the most suitable materials and tools completely free of charge!

In order to receive this discount card, you must provide an authorized store employee with a passport and a document confirming that you purchased a home or received a building permit no more than 18 months ago. Further, only the card holder (personalized card) or members of his family can use the card, but only upon presentation of an identification document or degree of relationship with the card holder.

At the end of the card's validity period (12 months), you will be given a cumulative discount card OMA Construction House, and the accumulated amount of previous purchases will affect the amount of the discount on the new card.

Pay special attention! The New House discount card is NOT valid in the online store and points of sale in Rogachev, Fanipoli, Slonim, Maryina Gorka and Stolin.

The discount amount on the OMA Construction House discount card directly depends on the amount accumulated on the card and ranges from 2% to 5%. A 2% discount is provided upon accumulation of an amount ranging from 100 BYN to 199.99 BYN. When accumulating amounts from 200 BYN to 399.99 BYN, the discount increases to 3%. To receive a 4% discount, you need to accumulate an amount in the range of 400-699.99 BYN. When you accumulate an amount of 700 BYN or more, you will receive a maximum discount of 5% on all OMA products, with the exception of promotional, discounted and special priced ones. When you accumulate an amount in excess of 7000 BYN, you will be provided with a VIP card with a 7% discount.

Ohm’s law for a section of a circuit can, of course, be described by the formula known from a school physics course: I=U/R, but I think it’s worth making some changes and clarifications.

Let's take a closed electrical circuit (Figure 1) and consider its section between points 1-2. For simplicity, I took a section of the electrical circuit that did not contain sources of emf (E).

So, Ohm's law for the section of the circuit under consideration has the form:

φ1-φ2=I*R, where

• I is the current flowing through a section of the circuit.
• R is the resistance of this section.
• φ1-φ2 ​​- potential difference between points 1-2.

If we take into account that the potential difference is voltage, then we arrive at the derivative formula of Ohm’s law, which is given at the beginning of the page: U=I*R

This is the formula of Ohm's law for the passive section of the circuit (containing no sources of electricity).

In an unbranched electrical circuit (Fig. 2), the current strength in all sections is the same, and the voltage in any section is determined by its resistance:

• U 1 =I*R 1
• U 2 =I*R 2
• Un=I*Rn
• U=I*(R 1 +R 2 +...+Rn

From here you can obtain formulas that are useful in practical calculations. For example:

U=U 1 +U 2 +...+Un or U 1 /U 2 /.../Un=R 1 /R 2 /.../Rn

The calculation of complex (branched) circuits is carried out using Kirchhoff's laws.

SIGN RULE FOR EMF

Before considering Ohm's law for a complete (closed) circuit, I will give a sign rule for EMF, which states:

If inside an EMF source the current flows from the cathode (-) to the anode (+) (the direction of the field strength of external forces coincides with the direction of the current in the circuit, then the EMF of such a source is considered positive (Fig. 3.1). Otherwise, the EMF is considered negative (Fig. .3.2).

A practical application of this rule is the possibility of bringing several sources of EMF in a circuit to one with the value E=E 1 +E 2 +...+En, naturally, taking into account the signs determined by the above rule. For example (Fig. 3.3) E=E 1 +E 2 -E 3.

In the absence of a back-to-back source E3 (in practice this almost never happens), we have a widespread serial connection of batteries, in which their voltages are summed.

OHM'S LAW FOR A COMPLETE CIRCUIT

Ohm's law for a complete circuit - it can also be called Ohm's law for a closed circuit, has the form I=E/(R+r) .

The above formula for Ohm's law contains the notation r, which has not yet been mentioned. This is the internal resistance of the EMF source. It is quite small, in most cases it can be neglected in practical calculations (provided that R>>r - the circuit resistance is much greater than the internal resistance of the source). However, when they are comparable, the value of r cannot be neglected.

As an option, we can consider the case in which R=0 (short circuit). Then the given formula for Ohm’s law for the complete circuit will take the form: I=E/r, that is, the value of the internal resistance will determine the short-circuit current. This situation may well be real.

Ohm's law is discussed here quite briefly, but the formulas given are sufficient to carry out most calculations, examples of which, as other materials are posted, I will give.

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The basic law of electrical engineering, with which you can study and calculate electrical circuits, is Ohm's law, which establishes the relationship between current, voltage and resistance. It is necessary to clearly understand its essence and be able to use it correctly when solving practical problems. Often mistakes are made in electrical engineering due to the inability to correctly apply Ohm's law.

Ohm's law for a circuit section states: current is directly proportional to voltage and inversely proportional to resistance.

If you increase the voltage acting in an electrical circuit several times, then the current in this circuit will increase by the same amount. And if you increase the circuit resistance several times, the current will decrease by the same amount. Similarly, the greater the pressure and the less resistance the pipe provides to the movement of water, the greater the water flow in the pipe.

In a popular form, this law can be formulated as follows: the higher the voltage at the same resistance, the higher the current, and at the same time, the higher the resistance at the same voltage, the lower the current.

To express Ohm's law most simply mathematically, it is believed that The resistance of a conductor that carries a current of 1 A at a voltage of 1 V is 1 ohm.

The current in amperes can always be determined by dividing the voltage in volts by the resistance in ohms. That's why Ohm's law for a circuit section is written by the following formula:

I = U/R.

Magic triangle

Any section or element of an electrical circuit can be characterized using three characteristics: current, voltage and resistance.

How to use Ohm's triangle: close the desired value - the other two symbols will give the formula for calculating it. By the way, Ohm's law is called only one formula from the triangle - the one that reflects the dependence of current on voltage and resistance. The other two formulas, although they are its consequences, have no physical meaning.

Calculations performed using Ohm's law for a section of a circuit will be correct when the voltage is expressed in volts, resistance in ohms and current in amperes. If multiple units of measurement of these quantities are used (for example, milliamps, millivolts, megaohms, etc.), then they should be converted to amperes, volts and ohms, respectively. To emphasize this, sometimes the formula for Ohm's law for a section of a circuit is written like this:

ampere = volt/ohm

You can also calculate the current in milliamps and microamps, while the voltage should be expressed in volts, and the resistance in kilo-ohms and mega-ohms, respectively.

Other articles about electricity in a simple and accessible presentation:

Ohm's law is valid for any section of the circuit. If it is necessary to determine the current in a given section of the circuit, then it is necessary to divide the voltage acting in this section (Fig. 1) by the resistance of this particular section.

Fig 1. Application of Ohm's law to a section of a circuit

Let's give an example of calculating current using Ohm's law. Suppose you want to determine the current in a lamp having a resistance of 2.5 Ohms, if the voltage applied to the lamp is 5 V. Dividing 5 V by 2.5 Ohms, we get a current value of 2 A. In the second example, we determine the current that will be flow under the influence of a voltage of 500 V in a circuit whose resistance is 0.5 MOhm. To do this, we express the resistance in ohms. Dividing 500 V by 500,000 Ohms, we find the value of the current in the circuit, which is equal to 0.001 A or 1 mA.

Often, knowing the current and resistance, voltage is determined using Ohm's law. Let's write the formula for determining voltage

U = IR

From this formula it is clear that the voltage at the ends of a given section of the circuit is directly proportional to the current and resistance. The meaning of this dependence is not difficult to understand. If you do not change the resistance of a section of the circuit, then you can increase the current only by increasing the voltage. This means that with constant resistance, greater current corresponds to greater voltage. If it is necessary to obtain the same current at different resistances, then with a higher resistance there should be a correspondingly higher voltage.

The voltage across a section of a circuit is often called voltage drop. This often leads to misunderstandings. Many people think that voltage drop is some kind of wasted unnecessary voltage. In reality, the concepts of voltage and voltage drop are equivalent.

Calculating voltage using Ohm's law can be illustrated with the following example. Let a current of 5 mA pass through a section of a circuit with a resistance of 10 kOhm and you need to determine the voltage in this section.

Multiplying I = 0.005 A at R -10000 Ohm, we get a voltage equal to 5 0 V. We could get the same result by multiplying 5 mA by 10 kOhm: U = 50 V

In electronic devices, current is usually expressed in milliamps and resistance in kilo-ohms. Therefore, it is convenient to use these units of measurement in calculations according to Ohm’s law.

Ohm's law also calculates resistance if the voltage and current are known. The formula for this case is written as follows: R = U/I.

Resistance is always a ratio of voltage to current. If the voltage is increased or decreased several times, the current will increase or decrease by the same number of times. The ratio of voltage to current, equal to resistance, remains unchanged.

The formula for determining resistance should not be understood to mean that the resistance of a given conductor depends on the outflow and voltage. It is known that it depends on the length, cross-sectional area and material of the conductor. In appearance, the formula for determining resistance resembles the formula for calculating current, but there is a fundamental difference between them.

The current in a given section of the circuit really depends on voltage and resistance and changes when they change. And the resistance of a given section of the circuit is a constant value, independent of changes in voltage and current, but equal to the ratio of these values.

When the same current passes in two sections of a circuit, and the voltages applied to them are different, it is clear that the section to which the greater voltage is applied has a correspondingly greater resistance.

And if, under the influence of the same voltage, different currents pass in two different sections of the circuit, then the smaller current will always be in the section that has greater resistance. All this follows from the basic formulation of Ohm’s law for a section of a circuit, i.e., from the fact that the greater the current, the greater the voltage and the lower the resistance.

We will show the calculation of resistance using Ohm's law for a section of a circuit using the following example. Let you need to find the resistance of the section through which a current of 50 mA passes at a voltage of 40 V. Expressing the current in amperes, we get I = 0.05 A. Divide 40 by 0.05 and find that the resistance is 800 Ohms.

Ohm's law can be clearly represented as the so-called current-voltage characteristics. As you know, a direct proportional relationship between two quantities is a straight line passing through the origin of coordinates. Such a dependence is usually called linear.

In Fig. Figure 2 shows, as an example, a graph of Ohm's law for a section of a circuit with a resistance of 100 Ohms. The horizontal axis represents voltage in volts, and the vertical axis represents current in amperes. The scale of current and voltage can be chosen as desired. A straight line is drawn so that for any point the ratio of voltage to current is 100 Ohms. For example, if U = 50 V, then I = 0.5 A and R = 50: 0.5 = 100 Ohm.

Rice. 2. Ohm's law (volt-ampere characteristic)

The graph of Ohm's law for negative values ​​of current and voltage has the same appearance. This indicates that the current in the circuit flows equally in both directions. The greater the resistance, the less current is obtained at a given voltage and the more flat the straight line is.

Devices in which the current-voltage characteristic is a straight line passing through the origin of coordinates, i.e., the resistance remains constant when the voltage or current changes, are called linear devices. The terms linear circuits and linear resistances are also used.

There are also devices in which the resistance changes when the voltage or current changes. Then the relationship between current and voltage is expressed not according to Ohm’s law, but in a more complex way. For such devices, the current-voltage characteristic will not be a straight line passing through the origin of coordinates, but will be either a curve or a broken line. These devices are called nonlinear.

Mnemonic diagram for Ohm's law

In 1826, the greatest German physicist Georg Simon Ohm published his work “Definition of the law according to which metals conduct contact electricity,” where he gives the formulation of the famous law. Scientists of that time greeted the publications of the great physicist with hostility. And only after another scientist, Claude Poulier, came to the same conclusions experimentally, Ohm’s law was recognized throughout the world.

– a physical pattern that determines the relationship between current, voltage and resistance of a conductor.It has two main forms.

Formulation Ohm's law for a section of a circuit – Current is directly proportional to voltage and inversely proportional to resistance .

This simple expression helps in practice to solve a wide range of issues. For better memorization, let's solve the problem.

Problem 1.1

The task is simple: finding the resistance of a copper wire and then calculating the current using the Ohm's law formula for a section of the circuit. Let's get started.

Formulation Ohm's law for a complete circuit - the current strength is directly proportional to the sum of the EMF of the circuit, and inversely proportional to the sum of the resistances of the source and circuit, where E is the emf, R is the circuit resistance, r is the internal resistance of the source.

Questions may arise here. For example, what is EMF? Electromotive force is a physical quantity that characterizes the work of external forces in an EMF source. For example, in a regular AA battery, EMF is a chemical reaction that causes charges to move from one pole to the other. The word itself is electro driving says that this force moves electricity, that is, charge.

Each has an internal resistance r, it depends on the parameters of the source itself. There is also a resistance R in the circuit; it depends on the parameters of the circuit itself.

The formula for Ohm's law for a complete chain can be presented in another form. Namely: the EMF of the circuit source is equal to the sum of the voltage drops on the source and on the external circuit.

To consolidate the material, we will solve two problems using the formulaOhm's law for a complete circuit.

Problem 2.1

Find the current strength in the circuit if it is known that the resistance of the circuit is 11 Ohms, and the source connected to it has an emf of 12 V and an internal resistance of 1 Ohm.

Now let's solve a more difficult problem.

Problem 2.2

The EMF source is connected to a resistor with a resistance of 10 Ohms using a copper wire 1 m long and a cross-sectional area of ​​1 mm 2. Find the current strength, knowing that the source emf is 12 V and the internal resistance is 1.9825 Ohms.

Let's get started.

Everything in this world lives and happens according to its own laws. Mowgli, the writer Kipling, lived by the law of the jungle, people live by their own written laws, and in the physics of electric current there are their own laws and one of these laws is called “Ohm’s law.” This is a very important law, one of the fundamental laws in the physics of electric current, and you must know and understand it if you want to understand electricity and electronics. I will try to help you and explain it to you, Ohm's law in simple words.

For the first time, the law was discovered and described in 1826 by the German physicist Georg Ohm, who showed (using a galvanometer) the quantitative relationship between electromotive force, electric current and the properties of the conductor as a proportional relationship. The law is named after this same Georg Ohm.

Now let's derive the definition of Ohm's law.

The amount of current in a section of the circuit is directly proportional to the voltage applied to this section of the circuit and inversely proportional to its resistance. Now let's look at this gobbledygook piece by piece. Part one - The amount of current in a section of the circuit is directly proportional to the voltage applied to this section of the circuit. In principle, everything is clear and logical, the higher the voltage connected to the circuit, the greater the current. The second part of the law is and is inversely proportional to its resistance. This means that the greater the resistance in the area, the less the current.

Ohm's law formula

In this formula - I - Current strength (Ampere), U - Voltage (Volts), R - Resistance (Ohm-).

I am attaching a comic drawing to this explanation; you might have seen it before on other sites, this is a very good “drawing - example”, many people use it on the pages of their sites.

How to find current strength, what is current strength - this means that if a voltage U = 1 Volt is applied to the ends of a conductor with a resistance of R = 1 Ohm, then the magnitude of the current I in the conductor will be equal to 1/1 = 1 Ampere.

I=U/R - current formula

U = IR - voltage formula

Resistance - if there is a voltage of 1 Volt at the ends of the conductor and a current of 1 Ampere flows through it, then the resistance of the conductor is 1 Ohm.

R = U/I - resistance formula

For ease of use of the formula, you can use the following “trick”.

By covering the triangle with your finger, the value that needs to be determined, we see the action that needs to be performed. For example - if you need to determine the resistance value, close - R

Now do you see what action needs to be performed? That's right, tension U divide by current I .

Formulas that you will definitely need.

I told you very briefly and in simple language about Ohm's law, but this is quite enough for you to be able to independently make calculations for your future electronic masterpieces in the first couple of days!