How to easily and simply convert milliamps to amperes and vice versa?

Charged particles, when moving longitudinally through a conductor, transfer an electric charge. The movement of charges is called electric current. In metal conductors this is the movement of electrons. The amount of charge transferred in the same period of time depends on the number of electrons and the speed of their movement.

Current strength when moving through the cross section of a metal conductor

What are amperes and milliamps

Ampere is a unit of measurement of current strength, a physical quantity equal to the ratio of the amount of charge to the time period of its passage through any surface or object; one of the 7 base units in the International System of Units (SI).

An ammeter is a device that measures in amperes.

Additional Information! The ampere was adopted as a unit of measurement in 1881 at the 1st International Congress of Electricians, held in Paris, and was named after the French physicist, mathematician and chemist André-Marie Ampere.

Andre Ampere

As amended in 2022, the International Committee of Weights and Measures provides the following definition of ampere:

“The magnitude of the ampere is established by fixing the numerical value of the elementary charge e to be 1.602176634×10^−19 when expressed in coulombs.”

Emblem of the International Committee of Weights and Measures

Milliamp is a fractional value, which, in accordance with its prefix, is equal to one thousandth of an ampere or 10^-3. It is also often written as “mamper” - this is a kind of average notation between its designation (mA) and name.

1 microamp equals 10^-6 A.

Important! Notation using the “milliA” type is not recommended; when using the designation of a unit of measurement, it is better to shorten the prefix with which it is used.

Table of prefixes and their meanings

Watt - unit of electrical power

Now it's time to move on to watts and find out what this quantity measures. “Do you have a powerful vacuum cleaner?” “Yes, almost two kilowatts!” Each of us, if not conducting such a dialogue himself, was certainly a witness to it. Are the phrases “kilowatt kettle” and “hundred-watt light bulb” familiar? Undoubtedly. Therefore, of course, you already guessed what is measured in watts. That's right - power. More precisely, electrical power. The more powerful the device, the more productive it is. The kettle boils faster, the light bulb shines brighter, the motor is faster and stronger than its low-power counterpart.

What this unit of measurement is needed for, I think, is clear to everyone - to assess the power of this or that electrical equipment. The more powerful it is, the more electricity it consumes.

Measurement technique

As noted earlier, ammeters, multimeters and testers are used to measure current. The first of them provide the greatest measurement accuracy. They measure only one quantity and only on one scale. And this is not entirely convenient. In turn, multimeters and testers allow you to measure almost all electrical quantities and not only in one range. Also, these devices have the ability to switch units of measurement. For example, the device indicates that the range has been exceeded. In this case, you need to switch milliamps to amperes and thereby find out the required value. The main disadvantage of testers and multimeters is that, unlike ammeters, their error is much greater. But still, in practice they are often used, since this makes it easy and simple to find a fault and fix it. Another important nuance associated with these devices: if previously it was necessary to break the circuit, now testers and multimeters have appeared that allow you to measure the current strength in a non-contact way, that is, without connecting. This solution is increasingly being used in practice.

Physical quantity

Ampere is a unit that quantifies the strength of current. Its value can be determined by taking direct measurements using a multimeter, tester or ammeter (direct method). The current strength is measured only by connecting the measuring device in series to the electrical circuit. In the second case, its value can be found out by performing calculations (indirect method). If you know the voltage applied to a section of the circuit, as well as its resistance, then it is enough to divide the first by the second - and we will get the required value. In practice, amperes are not used so often - this is a large value. Therefore, it is necessary to use multiple units - micro (10-6) and milli (10-3). But to carry out electrical calculations, you need to convert them into basic units of measurement (for example, milliamps to amperes). Consider the following example. The voltage on the circuit section is U = 6 V, and its resistance is R = 100 Ohms. Let us determine the current strength I on it according to Ohm’s law:

I = U/R, (1)

Where:

• U – voltage on the circuit section, V;
• R – resistance of the same section, Ohm;
• I is the current strength on it, A.

As a result of the calculations, we obtain I = U/R = 6/100 = 0.06 A. Not a very convenient number to understand. Therefore, it is recalculated into multiple units of measurement. In this case, it is convenient to represent this value in milliamps. To do this, multiply the resulting value of 0.06 A by 1000 and get 60 mA. You can also do a reverse conversion - milliamps to amperes. To do this, it is enough to divide 60 mA by 1000, and we get the same 0.06 A. From this recalculation we can see how many milliamps are in an ampere - 1000. Therefore, we divide or multiply by exactly this number. If the prefix “micro” is used, then to move from one unit of measurement to another you need to multiply or divide by 1,000,000.

Measurement technique

As noted earlier, ammeters, multimeters and testers are used to measure current. The first of them provide the greatest measurement accuracy. They measure only one quantity and only on one scale. And this is not entirely convenient. In turn, multimeters and testers allow you to measure almost all electrical quantities and not only in one range. Also, these devices have the ability to switch units of measurement. For example, the device indicates that the range has been exceeded. In this case, you need to switch milliamps to amperes and thereby find out the required value. The main disadvantage of testers and multimeters is that, unlike ammeters, their error is much greater. But still, in practice they are often used, since this makes it easy and simple to find a fault and fix it. Another important nuance associated with these devices: if previously it was necessary to break the circuit, now testers and multimeters have appeared that allow you to measure the current strength in a non-contact way, that is, without connecting. This solution is increasingly being used in practice.

Ampere strength (using two parallel conductors)

Imagine two infinite conductors that are located at a certain distance.
Currents flow through them. If currents flow in one direction, then the conductors attract. Otherwise, they will repel each other. The fields that parallel conductors create are directed counter to each other. And to understand why they react this way, you just need to remember that like poles of magnets or like charges always repel. To determine the directional side of the field created by the conductor, the right-hand screw rule should be used.

How to correctly measure electric current in amperes

It should be clarified that current measurement is a measurement of its basic characteristics (force and voltage). Most often, in laboratory or school conditions, the current strength on a conductor or in an entire electrical circuit is measured. To do this, use a special device - an ammeter. Which in the diagrams is correctly designated as a circle with the Latin letter “A” inside.

When connecting an ammeter, the following rules must be observed:

• Connect into an electrical circuit only in series with the section of the circuit where the current needs to be measured. In other words, before or after the section of the circuit for measurements.
• Be sure to observe the “signs” of the current in the circuit. The positive wire from the power source is connected to the positive side of the ammeter, and the negative wire to the negative side.
• Try not to exceed the value on the measurement scale, because in this case the device may fail. If the ammeter has 2 scales, then use the one with the larger permissible value limit.

Diagram of the correct connection of an ammeter to an electrical circuit
When measuring resistance, it is recommended to take into account the internal resistance of the ammeter itself, which is indicated on it. But at school they are usually neglected.

Additional Information! For measurements, a multimeter can be used - a device that combines the functionality of measuring force, power and other current parameters. It uses the same rules for connecting to a circuit as for an ammeter.

Current source

The water in the hose comes from a water supply, a spring with water in the ground - in general, not from nowhere. Electric current also has its own source.

The source can be, for example, a galvanic cell (a conventional battery). A battery works based on chemical reactions inside it. These reactions release energy, which is then transferred to the electrical circuit.

Any source necessarily has poles - “plus” and “minus”. The poles are its extreme positions. Essentially the terminals to which an electrical circuit is connected. Actually, the current flows from “+” to “-”.

What are amps, milliamps and microamps?

Correct designations: ampere - A, milliampere - mA, microampere - µA.

This physical quantity is named after the scientist’s surname, therefore, its notation will always contain the letter A in uppercase in the Russian designation, and the Latin letter A also in uppercase in the international designation.

Note! Do not confuse MA and mA, especially when solving problems. In the first case, it is designated megaampere (10^6 A), and in the second case, milliampere (10^-3 A), which is a billion times less than megaampere.

The spelling of submultiples and multiples of units, including milliamps and microamps, will be performed in accordance with the rules for writing units and prefixes established by the previously mentioned International System of Measurements (SI).

• The prefix is ​​written together with the name or designation of the unit.
• It is unacceptable to use two or more prefixes in a row (for example, micromilliampere).
• In most cases, it is customary to choose a prefix so that the number in front of it is in the range from 0.1 to 1000.

Additional Information! The prefix milli is translated from Latin (mille) as “thousand”. The prefix micro has ancient Greek roots (μικρός) and is translated as “small”.

How many watts are in 1 ampere?

To determine the power of a circuit, the concept of voltage is also important. This is the electromotive force that moves electrons. It is measured in volts. Most devices have this characteristic in their documentation.

To determine the power at a current of one ampere, you need to know the network voltage. So, for a 220 volt outlet it will be: P = 1 * 220 = 220 W. Formula for calculation: P = I*U, where I is current and U is voltage. In a three-phase network, a correction factor must be taken into account, reflecting the percentage of operating efficiency. In most cases it is between 0.67 and 0.95.

Ampere's Law - Definition

Conductors and dielectrics

Andre Ampère in 1920 defined the force with which a magnetic field affects a conductor placed in it. He established a direct relationship between the force arising around the conductor, the strength of the current, the magnitude of magnetic induction and the sine of the angle between the magnetic induction vector and the direction of the current. The expression looks like:

FA = B *I*L*sinα,

Where:

• FA – Ampere force, N;
• B – magnetic induction module;
• I – current strength, A;
• L – length of the conductor section, m.

The definition is valid for a conductor along which there is a constantly directed movement of electrons.

What is measured in amperes

The main physical quantity measured in amperes is current (denoted in formulas as “I”). As mentioned earlier in the definition of ampere, it is equal to the ratio of the amount of charge passing through a conductor over a certain time to the transit time itself.

Magnetomotive force (a physical quantity whose modulus shows the ability to create magnetic fluxes using electric currents) and magnetic potential difference (a scalar quantity characterizing the energy characteristics of the electrostatic field at a given point) are also measured in amperes. Often in practice you can find the term “ampere-turn” used to denote these quantities. But officially this is considered outdated terminology.

Additional units

In practice, for ease of recording, for very small or very large currents, multiple and submultiple units of the main one are often used. Let us recall that multiples are units that are much larger than the base, and submultiples are units that are much smaller than the base:

• Nanoamp - 1 nA = 0.000000001 = 1.0*10-9 A;
• Microamp - 1 µA = 0.000001 A;
• Milliamp - 1 mA = 0.001 A;
• Kiloampere - 1 kA = 1000 A;
• Megaampere - 1MA = 1000000 A = 1.0*106 A.

The International Bureau of Weights and Measures (located in Sèvres, France), which is responsible for ensuring the existence of the SI system, plans to introduce some changes in the definitions of base units in 2022. Changes will be made to the definitions of kelvin, kilogram, mole and ampere. This reform will not affect the lives of most people. The need for this event is caused by the requirements for increasing accuracy in scientific experiments and instrument making. Based on published documents, state standards will be developed and approved in countries using the SI system. At the next stage, adjustments will be made to school and university physics textbooks. The current definition of ampere, approved in 1948, is currently in force.

Rice. 3. Examples of ammeters

Current measurement in electrical circuits is carried out using ammeters. To calibrate the scales of these instruments (pointer and digital), the versatility and accuracy of the unit of measurement itself - the ampere - is very important.

Methods for converting current value

For modern energy-intensive household devices, currents of several amperes or more are quite workable, and the use of this unit of measurement does not cause difficulties. More economical devices include:

• Computers;
• Laptops;
• Smartphones and regular mobile phones;
• MP3 players, set-top boxes;
• LCD - lighting technology;
• LCD - video devices (monitors, televisions);
• Tablets;
• E-books;
• Navigators;
• Video recorders.

The characteristic consumption currents of these devices range from tens to hundreds of milliamps. To correctly convert amperes to milliamps, you should remember that the prefix “milli” means one thousandth of the base unit. Either 10 -3 or 0.001 can be used as a numerical multiplier. The use of such a multiple or submultiple unit is quite acceptable and legalized in domestic legislation in the form of GOST 8.417−2002 “Interstate standard. Units of quantities."

The abbreviated designation of the prefix “millie” in the Russian version is “m”, in the international version it is “m”. Thus, it is quite clear that 1000 milliamps equals 1 ampere.

Reactive load power calculation

All the above formulas are valid only for calculations in DC or AC circuits, but with an active load - an incandescent lamp, iron, electric kettle, heater, etc. If the current is alternating, and, say, an electric motor is used as a load (the same electric meat grinder, circular saw, electric drill, etc.), then the formula for calculating power has a slightly different form:

P = I x U x cos f , where f is the phase shift between the supply voltage and the consumed current in degrees. It is different for each device and the greater the greater the inductance or capacitance of the load. This value is usually given in the accompanying documentation for the device or directly on the nameplate of the device (the same electric motor).

Well, you have figured out what the relationship is between amperes and watts. It is enough to pick up a calculator and calculate the required values ​​using already known formulas.

How to correctly measure electric current in amperes

It should be clarified that current measurement is a measurement of its basic characteristics (force and voltage). Most often, in laboratory or school conditions, the current strength on a conductor or in an entire electrical circuit is measured. To do this, use a special device - an ammeter. Which in the diagrams is correctly designated as a circle with the Latin letter “A” inside.

When connecting an ammeter, the following rules must be observed:

• Connect into an electrical circuit only in series with the section of the circuit where the current needs to be measured. In other words, before or after the section of the circuit for measurements.
• Be sure to observe the “signs” of the current in the circuit. The positive wire from the power source is connected to the positive side of the ammeter, and the negative wire to the negative side.
• Try not to exceed the value on the measurement scale, because in this case the device may fail. If the ammeter has 2 scales, then use the one with the larger permissible value limit.

Diagram of the correct connection of an ammeter to an electrical circuit
When measuring resistance, it is recommended to take into account the internal resistance of the ammeter itself, which is indicated on it. But at school they are usually neglected.

Additional Information! For measurements, a multimeter can be used - a device that combines the functionality of measuring force, power and other current parameters. It uses the same rules for connecting to a circuit as for an ammeter.

Current direction

Previously, in physics textbooks they wrote this: once upon a time they decided that the current was directed from plus to minus, and then they found out that electrons flow through the wires. But these electrons are negative, which means they cannot go to minus. But since we’ve already agreed on the direction, let’s leave it as it is. The question then arose for everyone: why can’t the direction of the current be changed? But no one received an answer.

Now they write it a little differently: positive particles flow along the conductor from plus to minus, and the current is directed there. No one has any questions here.

How to convert milliamps to amps and vice versa

When converting values ​​from one quantity to another, you should be able to work with powers and the standard form of numbers in physics. It will be easier to translate if you know the correspondence of degrees and prefixes. It is recommended to master this.

To convert milliamps to amps, divide the given numeric value by 1000, or multiply by 10^-3 when working with the standard view. And for the reverse translation, you should either multiply by 1000 or multiply the value by 10^3.

Example: How many amps are in 500 milliamps?

A milliamp is 1000 times less than an ampere, which means you need to divide it by 1000; 500/1000 = 0.5. It turns out 0.5 A.

Converter

1 µA = 10^-6 A = 0.0000001 A. A microampere is a million times smaller than an ampere. To convert the first value to the second, you will need to divide by 1,000,000 or multiply by 10^-6 A.

To convert microamps to milliamps, you need to consider that 1 mA = 1000 µA. To convert values, the same steps will be used as for milliamps and amperes in the first algorithm.

Electricity is a vast topic in physics; to master it, you need to understand many processes and, above all, the basic unit that characterizes it - the ampere. And for the correct conversion of quantities, knowledge of the prefixes adopted in SI and mathematics is necessary.

Notes[ | ]

1. Magnetomotive force (undefined)
   . Great Soviet Encyclopedia. Archived from the original on August 21, 2011.
2. Le Système international d'unités (SI) / The International System of Units (SI). - BIPM, 2022. - P. 20, 132. - ISBN 978-92-822-2272-0.
3. ampere (A) (undefined)
   .
   www.npl.co.uk.
   _ Date accessed: May 21, 2022.
4. ↑ 1 2 History of the ampere
   , Sizes, 1 April 2014, . Retrieved January 29, 2017.
5. Kowalski, L, A short history of the SI units in electricity
   , Montclair, Archived copy from April 29, 2009 on the Wayback Machine
6. ↑ 12
   The SI brochure Description of the SI on the website of the International Bureau of Weights and Measures.
7. Regulations on units of quantities allowed for use in the Russian Federation. Basic units of the International System of Units (SI) (undefined)
   (unavailable link).
   Federal Information Foundation for Ensuring the Uniformity of Measurements
   . Rosstandart. Date accessed: February 28, 2022. Archived September 18, 2022.
8. Regulations on units of quantities allowed for use in the Russian Federation (undefined)
   (inaccessible link). Access date: December 28, 2014. Archived March 5, 2016.
9. Bodanis, David (2005), Electric Universe
   , New York: Three Rivers Press, ISBN 978-0-307-33598-2

Parameters of closing reed switches of standard and intermediate types

Notes

1. [bse.sci-lib.com/article072423.html Magnetomotive force]. Great Soviet Encyclopedia. [www.webcitation.org/6170yGWUP Archived from the original on August 22, 2011].
2. ↑ 12
   [www.bipm.org/en/publications/brochure/ The SI brochure] Description of the SI on the website of the International Bureau of Weights and Measures.
3. [www.leotec.ru/upload/iblock/432/432b148f277da39bdd5df10e1cd52d2d.pdf#page=3 GOST 8.417-2002. State system for ensuring the uniformity of measurements. Units of quantities.]
4. [www.sizes.com/units/ampHist.htm History of the ampere]
   , Sizes,
5. ↑ 12
   [www.bipm.org/utils/en/pdf/24_CGPM_Resolution_1.pdf On the possible future revision of the International System of Units, the SI] (English) Resolution of the XXIV General Conference on Weights and Measures (2011)
6. Here X stands for one or more significant figures, which will be determined in the final release based on the best CODATA recommendations
7. [www.bipm.org/en/CGPM/db/25/1/ On the future revision of the International System of Units, the SI] (English). Resolution 1 of the 25th CGPM (2014)
   . BIPM. Retrieved October 9, 2015.
8. [www.vniims.ru/download/879_postanovlenie.pdf Regulations on units of quantities allowed for use in the Russian Federation]

Literature

• Brief dictionary of physical terms / Comp. A. I. Bolsun, rector. M. A. Elyashevich. - Mn.: Higher School, 1979. - P. 23-24. — 416 p. — 30,000 copies.