Unit of electric current – what is an ampere and how do we measure It?
2025-09-29
Electric current is the orderly flow of electrons moving through a conductor under the influence of electric forces. For devices connected to the power grid to operate properly, the current supplied must meet specific parameters. One of the key values used to indicate the “quality” of electricity is its current intensity. But what exactly is the unit of electric current?
What is the unit of electric current? Basic information
The electric current describes the number of electrons flowing through a conductor’s cross-section over a given period of time. The higher the current, the more electrons reach the receiving point—meaning the device receives more electricity.
It’s important not to confuse current with voltage. While current expresses the amount of electrons passing through a conductor in a specific time unit, voltage defines the difference in electric potential between two points in a circuit—essentially the “speed” at which the electric charge moves. Both current and voltage must be balanced to deliver electricity with parameters suitable for connected devices.
Every conductor made of a specific material and cross-section can safely handle only a certain maximum current. Exceeding this limit may overheat and damage the wire. For this reason, electrical engineering continually searches for more durable conductors. For example, copper is standard in most devices, but silver and gold are even better conductors.
The SI unit of electric current
According to the International System of Units (SI), the unit of electric current is the ampere [A].
One ampere equals the flow of one coulomb (1 C) of charge per one second.
A coulomb corresponds to about 6.2415 × 10¹⁸ elementary charges (electrons), and a single elementary charge is approximately 1.6 × 10⁻¹⁹ C.
Measuring electric current
In practice, current can be measured with a multimeter, which can also measure voltage. Why measure current?
- To check if a device is operating correctly. User manuals or rating plates specify how much current the equipment should receive.
- To estimate power consumption and predict electricity costs.
Example:
If a lightbulb receives too little current, it will only glow dimly instead of shining brightly. In industrial machinery, insufficient current might prevent full functionality, while excess current can damage the electrical system.
Current measurement is most meaningful for devices that operate at a steady power level. Machines with variable loads will show fluctuating readings depending on real-time demand.
Is 1 ampere a lot?
For the human body, 1 A is extremely dangerous.
- Currents of 0.03 A (30 mA) can already cause harm.
- 0.30 A may impair respiratory muscles.
- 0.75 A can disrupt heart rhythm.
The danger depends not only on the current but also on the duration of exposure. Even 0.2 A can be hazardous if it flows through the body for more than a few seconds.
