# Ampere Prefixes; Definition, Conversion, Calculation

## Introduction

Ampere Prefixes are commonly used while studying electrical circuits. There are seven fundamental units i.e. metre(m), kilogram (Kg), second(sec), Ampere(A), Kelvin(K), mole(mol), and Candela (Cd). Among these basic units, Ampere(A) is used to denote the flow of current. It is also noted shortly as the amp. There are many systems of units used such as the KGS system, CGS system, and International SI system. Different systems assign different units for basic elements. Conversion of units can be done between different unit types. An ammeter is given to measure the flow of electric current in a circuit in ampere.

## What is Ampere?

Ampere is a unit used to denote current. It was denoted as amp and it was given by the name of Andre-Marie Ampere. He was a French physicist and mathematician who was also considered the father of electromagnetism. At first, it was defined as an electric current equivalent to 1019 elementary charges passing in 1.602176634 seconds. After the unit of charge was defined as the coulomb the unit Ampere was stated as one coulomb of charge passed per second.

$$\mathrm{1A = 1Csec^{-1}}$$

A - Ampere (unit of current)

C - Coulomb (unit of charge)

s - second (unit of time)

In the CGS (centimetre - gram - second system) system of units Ampere was stated as 1/10 of the unit of electric current. In the international SI system, one Ampere is known as the charge of one coulomb passing through a point per second.

## Prefixes of Ampere

Generally, prefixes are used to reduce the number of zeros in numerical equivalence. These zeros are reduced by using multiples and submultiples of units.

Submultiple of ampereMultiples of ampere
OrderSymbolNameOrderSymbolName
10-2cAcentiampere102hAhectoampere
10-3mAmilliampere103kAkiloampere
10-6μAmicroampere106MAmegaampere
10-9nAnano ampere109GAGiga ampere
10-12pApicoampere10-12TATera ampere
10-15fAfemtoampere1015PAPeta ampere

Table-1: Multiples and submultiples of units of Ampere

Among these most commonly used prefixes are A, kA, MA, mA, and μA. Conversion can be done between them.

## Ampere Conversion

Conversion of Ampere into milliampere

$$\mathrm{1000mA=1A}$$

For example, 4A is converted to milliampere by multiplying by 1000.

$$\mathrm{4×1000=4000\:mA}$$

Similarly, milliampere is converted into ampere divided by 1000.

$$\mathrm{3000\:mA=\frac{3000}{1000}=3A}$$

Conversion of Ampere into microampere

$$\mathrm{1000000\:\mu A=1A}$$

For example, 3A is converted to microampere by multiplying by 1000000

$$\mathrm{3×1000000=3000000\:\mu A}$$

Similarly, microampere is converted into ampere by divided by 1000000

$$\mathrm{400 \mu A=\frac{400}{1000000}=0.0004A}$$

Conversion of Ampere into kiloampere

$$\mathrm{1kA=1000A}$$

For example, 6A is converted to kA by dividing it by 1000

$$\mathrm{6A=\frac{6}{1000}=0.006kA}$$

Similarly, kA is converted into A by multiplying it by 1000

$$\mathrm{0.5kA=0.5×1000=500A}$$

Conversion of Ampere into Megaampere

$$\mathrm{1MA=1000000A}$$

For example, 400A is converted into MA by dividing it by 1000000

$$\mathrm{200A=\frac{200}{1000000}=0.002MA}$$

Similarly, MA is converted into A by multiplying it by 1000000

$$\mathrm{0.00007MA=0.00007×1000000=70A}$$

## Conversion of Watt, Volt, and Ohm into Ampere

Conversion of Watt into Ampere

Watt is a unit of power. Power is estimated by following the formula

$$\mathrm{Power(w)= Current(A)\times Voltage(V)}$$

Without the value of voltage watt cannot be converted to ampere. For example, if the power consumption is 3000 watts and the voltage applied to the circuit is 100V. Then,

$$\mathrm{Ampere=\frac{Power}{Voltage}=\frac{3000}{100}=30A}$$

Conversion of volt into Ampere

Volt is a unit of voltage. Here also it is not possible to convert volt into ampere without watt. For example, if the power consumption is 400W and the voltage applied to the circuit is 20V. Then,

$$\mathrm{Ampere=\frac{Power}{Voltage}=\frac{400}{20}=20A}$$

Conversion of ohm into Ampere

According to ohm’s law

$$\mathrm{Voltage(V)=Current(I)\times Resistance(R)}$$

On simplifying above equation, we get

$$\mathrm{I=\frac{V}{R}}$$

For example, the voltage across the circuit having resistance 6Ω is 36V then the current through the circuit is,

$$\mathrm{A=\frac{36}{6}=6A}$$

## Ammeter

Ammeter is an electronic instrument used to measure the current in the circuit. Generally current is measured in ampere. Hence it is named so. Ammeters are always connected in series in the circuit to measure current. Since it has a low resistance there is no voltage drop across it while measuring.

Ammeters used to measure smaller currents are in the milliampere (mA) or microampere (μA) range. Ammeters are used to measure both AC and DC current.

## Types of Ammeters

Ammeters are classified as below

• Moving coil ammeter

• Electrodynamic ammeter

• Moving iron ammeter

• Digital ammeter

• Hotwire ammeter

• Integration ammeter

### Moving Coil Ammeter

Moving coil ammeter is one of the ammeter types to measure the current through the circuit. It measures both AC and DC current. It uses magnetic deflection. Its name itself shows its function that the coil in this type rotates freely between permanent magnets. Interaction between the current given and the induced current makes the coil rotate and shows deflection.

### Electrodynamic Ammeter

It is also used to measure both AC and DC current with an accuracy of 0.10 to 0.25%. Here the field produced by a fixed coil is used to rotate a moving coil.

### Moving Iron Ammeter

It works on both alternating current and direct current. Here specially made soft iron is allowed to move freely in between the permanent electromagnets. It is further classified as repulsion and attraction.

### Digital Ammeter

In a digital ammeter the exact value of the current is shown on the display. Here a shunt resistance is included to calibrate the voltage in the circuit and using analog to digital converter current is shown in the display.

### Hot Wire Ammeter

It is used for both AC and DC power. It produces heat by passing a current through it which in turn extends the length of the wire.

## Conclusion

Ampere is a standard SI unit of current. current is defined as the flow of electric charge in an electric circuit. An ammeter is an instrument used to measure the current flow in the circuit. The ammeter measures the current in milliamperes as well as in microamperes. It measures the current in AC circuits as well as DC circuits. The current measured in amperes can be converted into milliamperes, microamperes, and nanometres as well as in watts and volts. There are different types of ammeters like moving coil ammeter, digital ammeters, and so forth available to measure the current from different sources.

## FAQs

Q1. What does Ampere denote?

Ans. Ampere is a unit used to denote current. It was denoted as amp and it was given by the name of Andre-Marie Ampere. He is a French physicist and mathematician who was also considered the father of electromagnetism. Ampere is stated as one coulomb of charge passed per second.

$$\mathrm{1A = 1C / 1s}$$

Q2. Give two advantages of digital Ammeter;

Ans. The advantages of digital ammeter are underneath

• Digital ammeters work in low power supply and their accuracy is very high.

• Reliable, economical and serve for a long time.

Q3. Why is the ammeter connected in series? What happens if it is connected in parallel?

Ans. The ammeter is an instrument used to measure the value of current in the circuit. It is measured in ampere. In a series connection, only the current passing through all the components is the same. That is why the ammeter is connected in series.

If it is connected in parallel the current through the circuit becomes high. Due to this high current more heat is produced which in turn affects the insulation of the wire.

Q4. What is the principle of moving coil ammeter?

Ans. Moving coil ammeter is one of the ammeter types to measure the current through the circuit. It measures both AC and DC current. It uses magnetic deflection. Its name itself shows its function that the coil in this type rotates freely between permanent magnets. Interaction between the current given and the induced current makes the coil rotate and shows deflection.

Q5. How to convert a moving coil galvanometer into an ammeter?

Ans. By connecting a low resistance in parallel with the moving coil galvanometer, it can be converted to an ammeter.

Updated on: 26-Apr-2023

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