The ampere is the SI unit of electric current that shows the amount of electric current flowing in an electric circuit. The electric current is proportional to the number of electrons flowing in a circuit. Therefore, one ampere is equal to the flow of one coulomb charge per second.
What is Ampere?
Ampere is named after the French Physicist and Mathematician Andre-Marie Ampere. It is defined as the number of electric charges moving in one second. In other words, the rate of flow of electric charge is the current. Coulomb is the unit of electric charge. one coulomb is equal to 6.24×1018 charge carriers.
If a 1-coulomb charge flow in one second, then the current flowing in the circuit is 1 ampere. The magnitude of the current increase with an increase of charge carriers in the circuit.
For example, if the 5-coulomb charge flows in one second in a circuit, then the current flowing in the circuit is;
Another definition of ampere can be given in terms of voltage(Force) and the resistance of the circuit. Thus, the ampere is the amount of current when the force of one volt acts through a one ohm resistance. The mathematical expression of the amount of current in a circuit is ;
For example, if the 10 volts are applied to a circuit that has 2 ohms resistance, then the current in the circuit is;
The dimension formula of the ampere is [M0 L0 T0 A1].
Ampere Unit Prefixes
The smaller units of the current are mA,μA, and nA. The larger unit of the current is kA.
| Current | Symbol |
| ampere | A |
| nanoampere | nA |
| microampere(microamps) | μA |
| milliampere(milliamps) | mA |
| kiloampere(kiloamps) | kA |
Ampere unit Conversion
| Unit of Current | Equivalent ampere |
| 1 ampere | 1 ampere |
| 1 nanoampere | 10-9A |
| 1 microampere | 10-6A |
| 1 milliampere | 10-3A |
| 1 kiloampere | 103A |
Conversion of amps (A) to kiloamps(kA) & Vice Versa
The kiloampere is the larger unit of current, and 1 kA = 1000 amps.
For example, 4 kA of current can be converted to amperes as follows:
4 × 1000 = 4000 amperes
For example, 10000 amperes of current can be converted to kA as follows:
10000 x 10-3 =10 kA
Conversion amps (A) to milliamps (mA) & Vice Versa
milliampere is the smaller unit of current. 1 mA is equal to-
1 milliampere = 10-3A, and 1 A= 1000 mA
For example, 50 milliamperes of current can be converted to amperes as follows:
50 × 10-3 = 0.05 amps.
For example, 2 amps. of current can be converted to milliamperes as follows:
2 x 1000 =2000 mA
Conversion of amps (A) to microamps (μA) & Vice Versa
microamperes is the smaller unit of current. It is much smaller than the milliampere.
1 μA = 10-6A , and 1 ampere = 1000000A = 106 μA
For example, 200 μA of current can be converted to amperes as follows:
200 x 10-6 =2 x 10-4 A= 20 mA
For example, 2amps current can be converted to microamperes as follows:
2 x 106 =2000000 amps.
Conversion of amps (A) to nanoamps (nA) & Vice versa
The nanoampere unit of the current is smaller than the microampere unit.
1 nanoampere = 10-9A , and 1 ampere = 109 nA
For example, 400 nano ampere of current can be converted to amperes as follows:
400 x 10-9 =4 x 10-7 A = 40μA
For example, 0.2 amperes of current can be converted to nano ampere as follows:
0.2 x 109 =2 x108 A
Conversion of Watt, Volt, and Ohm into amps(A)
We can calculate the current if the following data is available.
- The voltage and the resistance
- Watt and Resistance
Calculation of Amps with Volts and Ohms
As per ohm’s law
Solved Example
A circuit has 10Ω resistance and 20 volts is applied to the circuit. What is the current in the circuit?
Calculation of Amps with Watts and Volts
Watt is the power that is a multiplication of the voltage and the current.
Solved Example
A circuit draws 100 watts of power when connected to a 50 volts voltage source. Calculate the current in the circuit.
Calculation of Amps with Watts and Resistance
The power(P) of the circuit is equal to the product of the Square of the current(I) and the resistance(R).
Solved Example
A circuit draws 100 watts of power when its resistance is 4Ω. Calculate the current in the circuit.
