The movement of positively charged particles moving in a single direction is called current strength in physics. At its core, it is a physical quantity that demonstrates the charge that occurs at a certain time through a special conductor. There are several ways to find the current strength. The first is the calculation of the value according to the derived ready-made formulas in the presence of the initial data. The second is the use of special measuring instruments.
Content
- Why do you need current
- Calculation of the value by formulas
- Calculation of values by instrumentation systems
- Ammeter measurement
Why do you need current
The work of any electrical engineering is directly related to the physical size of charged particles. Knowing how to find the current strength allows you to understand the nuances of the operation of such equipment, a separate circuit or circuit. Calculation of such a value for a real professional will not cause any special difficulties, but for novice electricians this can cause some problems. To do this, it is worth knowing certain calculation formulas or having a special measuring device at hand.
In essence, there are several types of current. - it is permanent (contained in rechargeable batteries) and variable (located in the socket). It is the second type that is responsible for the lighting in the room, the operation of electrical appliances. The peculiarity of alternating current lies in fast transmission and transformation, a striking example of this is the operation of fluorescent lamps (the movement of current particles when turned on).
Calculation of the value by formulas
Since the most common type of current used in everyday life is alternating, then for its calculation, the calculation formula "Ohm's Law" known to every schoolchild is used. It looks like this - I = U / R (you can find the current by dividing the voltage by resistance), where:
- I is a variable current value;
- U is the voltage;
- R is resistance.
From this current formula, other equally useful calculations can be derived, which make it possible to determine other values, having only the actual indicators of the other two quantities (R = U / I and U = I * R). When calculating, it is recommended to use the basic units of measurement - amperes, volts and ohms. This calculation formula is most often used to calculate the force in resistive load circuits, for example, heaters, electric kettles, LEDs, etc.
In other cases, a different computational formula is used, containing power and voltage. It looks like this - I = P / U. Also, the current strength is calculated by the formula I = q / t, where q is the charge traveling along the conductor, measured in coulombs, and t is the time it takes for an electric charge to travel, calculated in seconds.
Calculation of values by instrumentation systems
In addition to formulas, in the absence of clear indicators of the required values, special instrumental systems are used. The advantage of this method is the speed and accuracy of the data obtained, minus the need to buy the required devices. The main ways to determine the current strength include:
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Magnetoelectric method of calculation, characterized by high sensitivity, accuracy of readings, minimum power consumption. It is often used to determine the value of the DC current. - Electromagnetic, the main computing element of which is a magnetomodular sensor, to which a signal is received from a magnetic field. In this way, you can find out the strength of direct and alternating current.
- Indirect, where a voltmeter is used in the old fashioned way, which determines the voltage readings at a certain resistance.
It should be noted that such methods are rarely used by electricians themselves, as they take a lot of time. It is much easier to use dedicated instrumentation rather than instrumental systems.
Ammeter measurement
The easiest way to find out the current strength is to measure the readings with an ammeter. The peculiarities of its use are in connecting the device to the breaks in the electrical circuit. For this, a suitable place is selected, after which it remains to wait until the ammeter screen displays the value of the current (charge) that has passed through the cable section after a certain time.
In addition to the classical device, analogs similar to them are used, designed to quickly find the current strength of small electricity - these are milliammeters, microammeters, galvanometers. The procedure for connecting the installation is not much different from conventional measuring instruments; they must be fixed in the section of the circuit where you want to know the value of the charge. Connection is made by several methods - serial and parallel. The whole process can be conventionally divided into several stages:
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preparation of the device from which a wire with two power cables comes out; - setting the required measuring range on the computing unit;
- applying one probe to the power supply wire of the device;
- connecting the second probe to any power supply contact;
- connecting the remaining wire to the second probe;
- turning on the measuring device;
- obtaining the value of the current strength shown on the meter.
When measuring the current strength, one must not forget that its type (variable or constant) plays a special role in this matter. Particular attention should be paid to the constant type of current, for example, if a power supply unit is installed inside the device, which reduces the mains voltage to lower values.
In this case, it is necessary to measure the current strength in the part of the circuit where the rectifying bridge of the diodes is installed.
An important role in the measurement is played by voltage; in this case, the measuring pins of the device are applied not to the open circuit, but to the parallel contacts of the power supply. It is also worth paying attention to the type of voltage, which is alternating and constant.
