Content:

Electric current is generated in order to further use it for certain purposes, to perform any work. Thanks to electricity, all devices, devices and equipment function. The work itself is a certain effort applied to move an electric charge a certain distance. Conventionally, such work within the circuit section will be equal to the numerical value of the voltage in this section.

To perform the necessary calculations, it is necessary to know how the work of the current is measured. All calculations are carried out on the basis of the initial data obtained using measuring instruments. The larger the charge, the more effort is required to move it, the big job will be done.

What is called the work of the current

Electric current, as a physical quantity, in itself has no practical significance. Most an important factor is the action of the current, characterized by the work performed by it. The work itself is a certain action in the process of which one type of energy is converted into another. For example, electrical energy with the help of rotation of the motor shaft is converted into mechanical energy. The work of electric current is the movement of charges in a conductor under the influence of an electric field. In fact, all the work of moving charged particles is done by an electric field.

In order to perform calculations, the formula for the work of an electric current must be derived. To draw up formulas, you will need parameters such as current strength and. Since the work of an electric current and the work of an electric field are the same thing, it will be expressed as the product of voltage and charge flowing in a conductor. That is: A = Uq. This formula was derived from the ratio that determines the voltage in the conductor: U = A/q. It follows that the voltage is the work of the electric field A on the transfer of a charged particle q.

The charged particle or charge itself is displayed as the product of the current strength and the time spent on the movement of this charge along the conductor: q \u003d It. In this formula, the ratio for the current strength in the conductor was used: I \u003d q / t. That is, is the ratio of the charge to the time interval for which the charge passes through the cross section of the conductor. In its final form, the formula for the work of an electric current will look like a product of known quantities: A \u003d UIt.

In what units is the work of electric current measured?

Before directly solving the question of what the work of the electric current is measured in, it is necessary to collect the units of measurement of all physical quantities with which this parameter is calculated. Any work, therefore, the unit of measurement of this quantity will be 1 Joule (1 J). Voltage is measured in volts, current is measured in amps, and time is measured in seconds. So the unit of measurement will look like this: 1 J = 1V x 1A x 1s.

Based on the units of measurement obtained, the work of the electric current will be determined as the product of the current strength in the circuit section, the voltage at the ends of the section and the time interval during which the current flows through the conductor.

The measurement is carried out using a voltmeter and a watch. These devices allow you to effectively solve the problem of how to find the exact value of a given parameter. When you turn on the ammeter and voltmeter in the circuit, it is necessary to monitor their readings for a specified period of time. The resulting data is inserted into the formula, after which the final result is displayed.

The functions of all three devices are combined in electric meters that take into account the energy consumed, and in fact the work done by the electric current. Here, another unit is used - 1 kWh, which also means how much work was done during a unit of time.

Etc. To do this, electrical networks are laid in each apartment, the voltage in which is supported by sources current.

Can be defined work current in proportion to his strength. So, the charge passes through a section of the circuit for a certain period of time equal to t. You can find its value by calculating the product of the force current to this parameter: q = I t.

Substitute the resulting expression into the main formula: A = U I t.

Unit of work current in the SI system is 1 Joule, named after the British physicist who deduced the connection of thermal energy with mechanical work. 1 Joule is equivalent to a unit of energy generated in a stationary electric field by a force current in 1 ampere, voltage 1 watt for 1 second of time.

There is also a so-called off-system unit of work current, which is expressed in kWh (kilowatt hour). It is she who is used in the calculation of electricity in domestic and office premises and is indicated in the documents for paying utility bills. 1 kWh is equal to 3,600,000 Joules or 3,600 kJ.

Electricity is the work of force current, which takes place over a certain time interval and is consumed by household appliances. In order for them to consume its minimum amount and, therefore, save the budget, it is necessary to pay attention to another characteristic when buying current- power. This value is equal to the work current performed per unit of time.

The simplest transformer current(TT) consists of two copper windings, isolated from each other and wound on a steel core. Each of the windings has a certain number of turns, the ratio of which determines the transformation ratio current. Errors that arise when converting the primary current into the secondary one, allow us to attribute the CT to one of the accuracy classes.

Instruction

Currently, there is a huge variety of TT. There are several classifications: by installation site, by design, by type of insulation, etc. It will be quite difficult for a person unprepared in this area to immediately determine which type this or that TT belongs to. The easiest way to determine the type of TT is to decipher the symbol indicated on the plate attached to the TT itself (see Fig. 1).

However, very often, for some reason, there is no nameplate with factory data on the CT case. In this case, you can use the factory documentation. Find a passport-protocol for this type of equipment. The type of CT will be indicated on its first page. In addition, the required information is often specified in the principal electrical diagrams given connection (chain).

In the event that this method does not give the desired result, you can try to load this CT, that is, remove the current-voltage characteristic from it. This will require special equipment: a loading unit, current clamps, a voltammeter-phase meter (VAF), an AC voltmeter current.

For correct readings, it is necessary to apply current either to the terminals of the primary winding (large current) and take values current and voltage from the secondary winding, or, conversely, apply a small current to the terminals of the secondary winding of the CT, and remove large values ​​​​from the primary current and tension. Then, according to the data obtained, you will need to build curves that determine the dependence of voltages on primary and secondary currents, as well as determine the transformation ratio current and the absolute error of this CT.

By appearance and the received data, using reference materials, you can approximately determine the type of a given CT, its condition (healthy/faulty), as well as the accuracy class. However, in order to avoid mistakes, it is still better to contact a qualified specialist. It will not only save you time, but also give you advice on how to use, how to connect and maintain this device.

Very often a situation arises when it is necessary to adjust the operation of a device. The master of the desired profile may not always be nearby, so you have to do the repairs yourself. But in order for the device to work, and you do not get injured, you need to know what you are dealing with. That is, you need to determine the current parameters, and first of all - voltage.

You will need

• Voltmeter, multimeter, ammeter

Instruction

Determine if you are measuring a constant or a variable voltage. Switch the avometer or multimeter to DC or AC mode. Most often, it is necessary to measure voltage power or electromotive force (EMF). Even if the approximate parameters of these voltages are unknown, then at the initial stage of the measurement, the device must be switched on to the maximum voltage measurement mode. Connect the device according to the polarity.

When studying the use of electric current, you need to be able to calculate the amount of electricity that is spent on a particular action - heating water in an electric kettle, lifting an elevator, etc. That's why we derive a formula for a convenient calculation of the work of the current.

In the left parts of the equalities there are different symbols, but they denote the same physical quantity - power. Therefore, the right parts of the formulas can be equated: I U = A / t . Let's express the work:

This formula calculates current work or, which is the same, consumed electricity. Please note that these terms are synonymous.
When a source of electrical energy appears in the circuit, it electric field sets the charged particles inside the conductor (electrons and/or ions) in motion, and their energy increases. The sum of the energies of all particles of the body is the internal energy of the body (see § 7-e), which means that the internal energy of the conductor at the moment of occurrence of current in it increases. According to the first law of thermodynamics (see § 6-h), internal energy can be spent on heat transfer or making mechanical work. But, being spent, it is constantly replenished due to the energy of the current source.
The passage of current through the conductor - the work of the current - is always accompanied by current actions(see § 8-h). At the same time, electricity is necessarily converted into other types of energy: thermal (for example, an iron, a kettle), mechanical (for example, a vacuum cleaner, a fan), and so on. That's why by the expression "current does work" we mean the conversion of electricity into other forms of energy. In this case, the work of the current and the consumed electricity are synonymous expressions.
To measure the consumed electricity, special measuring instruments are used - electricity meters .
To account for the consumed electricity, a larger unit of work is used instead of the joule - kilowatt-hour(symbol: 1 kWh). For example, the meter in the figure shows a value of 254.7 kWh. This may mean, for example, that for the entire time of accounting, a consumer with a power of 254.7 kW worked for 1 hour or that a consumer with a power of 2547 W worked for 100 hours (and so on, observing the proportion).

Let's find this connection units of work with a more familiar unit for its measurement - the joule.
1 kW h = 1000 W 60 min =
\u003d 1000 J / s 3600 s \u003d 3 600 000 (J / s) s \u003d
= 3,600,000 J = 3.6 MJ
So, 1 kWh = 3.6 MJ.
Formula A = IUt will help us find out what the physical meaning of the quantity "electric voltage" is. Let's express it from a formula.

It can be seen from this that 1 volt is such a voltage at which a current of 1 ampere is capable of producing 1 joule of work in 1 second. In other words, electrical voltage shows the work that the forces of the electric field do every second to maintain a current of 1 ampere in the circuit.
In addition, from the formula I = q / t(see § 9-b) it follows that q = I t. Then:

Based on this formula, 1 volt can also be considered as such a voltage at which the work of the forces of the electric field when moving a charge of 1 C along a conductor will be equal to 1 J.
Based on the whole "below the line" reasoning, we will say that electric voltage is one of the characteristics of an electric field that moves charges along a conductor.