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.
1A=1Csec−11A=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.
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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 ampere | Multiples of ampere | ||||
|---|---|---|---|---|---|
| Order | Symbol | Name | Order | Symbol | Name |
| 10-1 | dA | deciampere | 101 | daA | Deca ampere |
| 10-2 | cA | centiampere | 102 | hA | hectoampere |
| 10-3 | mA | milliampere | 103 | kA | kiloampere |
| 10-6 | μA | microampere | 106 | MA | megaampere |
| 10-9 | nA | nano ampere | 109 | GA | Giga ampere |
| 10-12 | pA | picoampere | 10-12 | TA | Tera ampere |
| 10-15 | fA | femtoampere | 1015 | PA | Peta 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
1000mA=1A1000mA=1A
For example, 4A is converted to milliampere by multiplying by 1000.
4×1000=4000mA4×1000=4000mA
Similarly, milliampere is converted into ampere divided by 1000.
3000mA=30001000=3A3000mA=30001000=3A
Conversion of Ampere into microampere
1000000μA=1A1000000μA=1A
For example, 3A is converted to microampere by multiplying by 1000000
3×1000000=3000000μA3×1000000=3000000μA
Similarly, microampere is converted into ampere by divided by 1000000
400μA=4001000000=0.0004A400μA=4001000000=0.0004A
Conversion of Ampere into kiloampere
1kA=1000A1kA=1000A
For example, 6A is converted to kA by dividing it by 1000
6A=61000=0.006kA6A=61000=0.006kA
Similarly, kA is converted into A by multiplying it by 1000
0.5kA=0.5×1000=500A0.5kA=0.5×1000=500A
Conversion of Ampere into Megaampere
1MA=1000000A1MA=1000000A
For example, 400A is converted into MA by dividing it by 1000000
200A=2001000000=0.002MA200A=2001000000=0.002MA
Similarly, MA is converted into A by multiplying it by 1000000
0.00007MA=0.00007×1000000=70A0.00007MA=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
Power(w)=Current(A)×Voltage(V)Power(w)=Current(A)×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,
Ampere=PowerVoltage=3000100=30AAmpere=PowerVoltage=3000100=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,
Ampere=PowerVoltage=40020=20AAmpere=PowerVoltage=40020=20A
Conversion of ohm into Ampere
According to ohm’s law
Voltage(V)=Current(I)×Resistance(R)Voltage(V)=Current(I)×Resistance(R)
On simplifying above equation, we get
I=VRI=VR
For example, the voltage across the circuit having resistance 6Ω is 36V then the current through the circuit is,
A=366=6AA=366=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.
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