Electric current

Electric current definition, units and the effects produced

Electric current is the transport of electric charge. The transport of this flow of electric charge occurs mainly through the movement of negatively charged electrons through conductors and semiconductors under the influence of an electric potential difference.

In electricity, positive charge carriers, the movement of ions in an electrolyte or plasma, also cause an electrical current. In all these cases, the transport of electrical energy is carried out through the movement of electrical charges. Furthermore, an electric current is also created as a change in the flow of electrons, such as between the plates of a capacitor during charging and discharging, without moving the charge carriers.

The two main types of electrical current are:

  1. Direct current (DC); for example, in electronic circuits, charges flow in direct current.

  2. Alternating current (AC); for example, the public electric network uses this type of current to transport electricity.

What are the three effects that an electric current can produce?

An electric current can produce:

  • Chemical reactions: One technique to produce chemical reactions using electric current is electrolysis. Electrolysis uses electric current to cause an oxidation-reduction reaction. 

  • Heating effects on the conductor. It occurs due to the Joule effect, a phenomenon by which the moving electrons of an electric current impact the conducting material. The kinetic energy that the electrons have is then converted into thermal energy, heating the material through which they circulate.

  • Magnetic effects are caused by the electric field. According to the studies done by Hans Christian Oersted, when charges move to throw a conductor or a conducting solution, they generate an electric field that has the same effects as magnets.

What is the SI unit of the electric current?

The unit of measure for electric current in the international system of units is the coulomb (C).

The coulomb is defined from a current measurement as: “1 coulomb of charge is the amount of electrical charge that passes through a  section in 1 second by the amperage of 1 ampere:

1C = 1A·1s

What is the formula for the electric current?

Ohm's law determines the formula for electric current:

V = R·I


  • “R” is the electrical resistance, the obstacle that the flow of electrons encounters in an electric circuit, for example, an electric motor. The unit of measure for resistance is ohms (Ω).

  • “I” is the intensity of the electrical current flowing expressed in Amperes (A).

  • “V” is the voltage, the potential difference between one point to another expressed in Volts (V).

What is the direction of the electric current?

In a metal conductor, negatively charged free electrons move from the negative terminal (electron surplus and lower potential) to the positive terminal (electron deficiency, higher potential).

Traditionally, electric current is expressed as the displacement of positive charge. However, when it was learned that electric current is generally caused by electrons moving in the opposite direction, the electron was assigned, by definition, a negative charge.

The old definition of flow direction, therefore, remained in effect.

How is current measured?

The most used devices to measure an electric current are:

The ammeter

An ammeter is used to measure electric current. The ammeter is connected in series with the circuit to be measured. In order not to influence the circuit to be measured too much, the instrument must cause as little voltage loss as possible.

Electric current definition, units and the effects produced

The clamp meter.

Another method of measuring electrical current is with a current clamp or a clamp meter. A clamp meter is a measuring instrument for alternating current, designed as a clamp that is clamped around a current-carrying conductor.

In the clamps, the magnetic field created around the conductive material induces a current, a measure of the current flowing through the clamped conductor.

Transmission loss 

From a distant power plant to the place of consumption (each consumer), some electric energy is consumed as Joule heat due to the resistance of transmission lines and distribution lines, resulting in energy loss.

Since this loss increases in proportion to the square of the amount of current while the electric current is passed, the transmission side reduces the amount of current by increasing the voltage to reduce the loss.

A transformer gradually reduces the voltage in power transmission networks and distribution networks as it approaches the customer. Alternating current is currently used for most power transmissions because transformers can quickly raise or lower the voltage. Reducing the transmission loss rate contributes to saving energy resources for power generation by reducing the amount of power generated.

Data de publicació: October 7, 2019
Última revisió: May 26, 2022