Operation and power of electric current

In each closed circuit, a double energy conversion necessarily takes place. In the current source, a modification of some energy (for example, in the generator - a mechanical one) is made into an electrical one, and in the current circuit it again turns into an equivalent amount of energy of a different kind. The measure of the transformation into the current circuit of electricity into any other types of energy is the magnitude of the work of the current.

But we understand that the work and power of the electric current is the work of the electric field forces moving the charges; So it is easy to calculate.

The work on the transfer of electric charge in an electric field is estimated by the product of the transferred charge by the magnitude of the potential difference between the points at the beginning and the end of the transfer, i.e. By the voltage value:

A = qU.

Obviously, this relationship can be applied to the evaluation of such concepts as the work and power of electric current. The magnitude of the charge flowing in the circuit can be judged from the current flowing in the circuit and the time it takes, since q = It.

Using such a relation, we obtain a formula expressing the magnitude of the operation of the current on a particular section of the circuit having a voltage U:

A = UIt.

The work and power of the electric current are measured as follows: if the current is measured in amperes, the operating time in seconds, and the voltage in volts, then the work is in joules (J).

Thus, 1 joule = 1 ampere x 1 volt x 1 second.

Power is measured in watts (watts):

1 watt = 1 joule / 1 second, or 1 watt = 1 volt x 1 ampere.

The question of calculating the magnitude of the work of the current in this region is completely unrelated to the question of what form of energy the electric energy will turn into in this section. This work is a measure of electricity converted into other types.

Electric current, when performing work, can inflame the filament of an electric lamp, melt metals, rotate the motor's armature, cause chemical transformations, etc. In all cases, the work and power of the electrical current determine the level of electricity conversion into other forms - mechanical energy, thermal energy, etc.

Knowing that the power P = A / t, it is possible to obtain a formula by means of which the current is calculated on a particular section of the circuit:

P = UI.

The work and power of a direct current can be calculated with the help of these formulas, and also with the help of an ammeter, a voltmeter. In practice, the work of the electric field is measured with a special meter. Passing through the counter, a light aluminum disk starts to revolve inside it , and its speed will be directly proportional to the current and voltage. The number of turns that he will make in a certain time, will help to draw conclusions about the work accomplished during this time. Electricity meters can be seen in every apartment.

The power of the current is measured using a special instrument - a wattmeter. In the device of this device, the principles of a voltmeter and an ammeter are combined.

On many electrical devices and technical devices, their power is indicated. For example, the power of an incandescent bulb can be 25 W, 75 W, etc., the power of a vacuum cleaner or an iron of about 1000 W, the power of electric motors can reach very high values - up to several thousand kilowatts. In this case, we mean the power of the current that passes through this or that device.

The operation and power of the alternating current are calculated differently. So, to calculate the work done by an alternating current for a certain period of time, you can use the formula:

P = 1 / 2I₀U₀ cos φ. Often this formula is written in the form: P = IU cos φ, where I and U are the values of voltage and current strength, which is 2 times less than the corresponding amplitude values.

The formula for calculating the AC power will be the same as for the constant.

Units of energy and work:

1 watt-second = 1 J 1 watt-hour = 3600 J;

1 hectawatt-hour = 360000 J;

1 kilowatt-hour = 3600000J.

Power Units:

1 ampere-volts = 1 W;

1 hectare = 100 W;

1 kilowatt = 1000 watts.