1 ampere = how many ma

The ampere is the SI base unit for electric current in the metric system. An ampere is sometimes also referred to as an amp. Amperes can be abbreviated as A ; for example, 1 ampere can be written as 1 A.

Ohm's Law states the current between two points on a conductor is proportional to the voltage and inversely proportional to the resistance. Using Ohm's Law, it's possible to express the current in amperes as an expression using resistance and voltage. The current in amperes is equal to the potential difference in volts divided by the resistance in ohms. You are here. The current definition of the ampere has been in place since but may change in the near future.

As the SI base unit of electric current, the ampere is used worldwide for almost all applications involving electric current. The definition of some SI base units may change in the near future. Although the definitions of some units may change, the actual size of the units would remain the same; the change in definition will not have much, if any, effect on the daily use of these units.

The ampere is one of the units being considered for re-definition due to the difficulty of maintaining high precision in practice. The proposed re-definition of the ampere involves using a fixed numerical value of elementary charge of 1. This definition would also be based on the re-definition of the second which would be defined as the fixed numerical value of cesium frequency.

A milliampere symbol: mA is a submultiple of the SI base unit of electrical current, the ampere. One of the first generators that had practical use was the magneto-electric generator created by the German and Russian researcher Moritz von Jacobi who worked in Russia from to It was used by the Russian Army navy mine squads to inflame the fuses of the naval mines. Improved generators of this type are used to this day to activate mines, and they can be often seen in WWII movies, where guerilla fighters or saboteurs use them to blow up bridges, derail trains, and in other similar applications.

From then on leading engineers competed with each other to improve AC and DC generators, with the ultimate stand-off between the two titans of the modern field of generating electricity, with Thomas Edison of General Electric on one side, and Nicola Tesla of Westinghouse on the other. This provided a significant push to propel the economy of the USA and brought the country to the leading position in the world. In addition to the ability to generate electricity for various needs, which depended on the conversion of mechanical movement into electricity due to the reversibility of the electric machines, another possibility of reverse conversion of electric current into mechanical movement became a reality.

This was done by electrical engines that worked on DC and AC current. You could say that these types of machines are some of the most widely used technologies, and they include car and motorcycle starters, drives of commercial machines and machine tools, and consumer devices and electronics.

We became skillful at various tasks such as cutting, drilling, and shaping thanks to these devices. We use optical discs such as CDs and hard drives in our computers thanks to these technologies as well — without them, we would not have been able to create the miniature precision DC electric motors.

In addition to the electromechanical engines that we are used to, ion thrusters also work thanks to the electric current. These engines use the principle of propulsion by emitting of accelerated ions of a given substance. They are currently used in space mainly for taking small satellites to the orbit. It is very likely that the future technologies of the 22nd century such as photonic laser thrusters, which are still being designed and which will take our interstellar ships at speeds approaching the speed of light, will also depend on electric current.

Another use for the generators of DC current is for growing crystals for electronic components. This process requires extra stable generators of DC current.

Such precision solid-state generators of electric current are called current stabilizers. We should note that devices for measuring electric current, such as microammeters, milliammeters, and ammeters, are quite different from each other, depending on their structure and the measuring principles that they use. They include direct current ammeters, low-frequency alternating current ammeters, and high-frequency alternating current ammeters.

The measuring mechanisms of these devices can be subdivided into a moving coil, moving iron, moving magnet, electrodynamic, induction, hot-wire, and digital ammeters. Most of the analog ammeters include a movable or a stationary frame with a wound coil and stationary or movable magnets. Due to this structure, a typical ammeter has an equivalent circuit that is a connection in series of an inductor and a resistor with a capacitor attached in parallel to them.

Due to this, analog ammeters are not sensitive enough to measure high-frequency current. The basic measuring device for an ammeter consists of a miniature galvanometer. Its measurement ranges are created by using additional shunt resistors with small resistance, and this resistance is lower than that of the regular galvanometer.

This way, using one device as a base, it is possible to create various measuring devices for measuring currents with different ranges, including microammeters, milliammeters, ammeters, and even kiloammeters. In general, in electrical measurements the behavior of the current is important.

It could be measured as a function of time and be of different types, for example constant, harmonic, aharmonic, pulse, and so on. Its magnitude characterizes the way the electronic circuits and devices work. The following values for current are identified:. Instantaneous current I i is the value of the current at any given time.

It can be viewed on the screen of an oscilloscope and measured for every moment in time by looking at the oscilloscope. Peak-to-peak amplitude current I m is the largest instantaneous value of current for a given time period.

Root mean square amplitude value of current I is found as a square root of the arithmetic mean of the squares of instantaneous currents for a period of the waveform. Mean value of current is a mean of all of the values of instantaneous current for the duration of the time being measured.

The difference between the maximum and the minimum value of electric current is known as the peak-to-peak value of a signal. These days it is common to use multimeters and oscilloscopes to measure the electric current. Both of these devices provide information not only about the shape of the current or voltage but also about other important characteristics of the signal.

These include the frequency of the periodic signals, and this is why it is important to know the frequency limit of the measuring device when measuring electric current. Let us illustrate the above with a series of experiments for measuring the active and the peak values of the current of the sinusoidal and the triangular signals. We will use a generator of signal, an oscilloscope, and a multimeter. The signal generator FG is connected to the load, which consists of a multimeter MM connected in series with a shunt Rs and a load resistor R.

The oscilloscope OS is connected in parallel to the shunt resistor R s. While doing this experiment, let us keep in mind that the working frequency of the oscilloscope is much higher than the working frequency of the multimeter. Let us supply to the load resistor a sinusoidal signal, with a frequency of 60 Hz and amplitude of 9 V. Modern oscilloscopes have a very convenient Auto Set button, which allows displaying any measured signal without touching any other oscilloscope control.

Let us press the Auto Set button and watch the signal on the screen, as in illustration 1. Here the range of the signal is about five large divisions, and the value of each division is mV. The multimeter shows the value of electric current as 3. Note that the range of the current through our circuit made from two resistors and a multimeter in series equals.

Let us double this value — we get 8. Now let us reduce the generated signal in half. The range of the signal on the oscilloscope will also be reduced roughly in half mV , and the multimeter will show the value that is also roughly reduced in half and equals 1.

Let us determine the value of the active current on the oscilloscope:. Now let us increase the frequency of the generator to 10 kHz. The picture on the oscilloscope will change, but the range of the signal will stay the same. The value on the multimeter will decrease — this is due to the frequency range of the multimeter. Let us use the initial frequency of 60 Hz and voltage of 9 V again, but let us change the shape of the signal on the generator from sinusoidal to triangular.

The range of the signal on the oscilloscope stays the same, but the value on the multimeter decreases compared to the value of the current that it showed in Test 1.

This is because the root mean square value of the current has changed. This article was written by Sergey Akishkin. Do you have difficulty translating a measurement unit into another language?

Help is available! Post your question in TCTerms and you will get an answer from experienced technical translators in minutes. In this part of the TranslatorsCafe. Electric current is a flow of electric charge through a conductive medium.

In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma. The SI unit for measuring the rate of flow of electric charge is the ampere , which is defined by taking the fixed numerical value of the elementary charge e to be 1.

This online unit converter allows quick and accurate conversion between many units of measure, from one system to another. The Unit Conversion page provides a solution for engineers, translators, and for anyone whose activities require working with quantities measured in different units.

Learn Technical English with Our Videos! You can use this online converter to convert between several hundred units including metric, British and American in 76 categories, or several thousand pairs including acceleration, area, electrical, energy, force, length, light, mass, mass flow, density, specific volume, power, pressure, stress, temperature, time, torque, velocity, viscosity, volume and capacity, volume flow, and more. Note: Integers numbers without a decimal period or exponent notation are considered accurate up to 15 digits and the maximum number of digits after the decimal point is In this calculator, E notation is used to represent numbers that are too small or too large.

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