8.3. Electric variables.

In the context of electrical circuits, a circuit variable is any measurable quantity that can describe the behavior or characteristics of a circuit. Circuit variables can include quantities such as voltage, current, resistance.

Circuit variables can be used to analyse and comprehend a circuit's behaviour, and they can be altered and controlled to accomplish specific results. Changing the voltage or current in a circuit, for example, can change the behaviour of components like resistors, capacitors, and inductors, affecting the overall performance of the circuit.

Circuit variables can be measured with voltmeters, ammeters, and multimeters and estimated with mathematical formulas and laws such as Ohm's law.

Current (I)

is the variable that tells us how many electrons flow through the cross-section of a conductor per unit of time. Its unit of measurement in the International System is the ampere (A).

Voltage (V) 

is the variable that tells us the difference in electrical energy per unit of charge between two points in a circuit. This difference can also be called the electric potential difference, potential drop or electric tension. Its unit of measurement in the International System is the volt (V). To indicate the energy delivered by power sources to the circuit per unit of charge, the term electromotive force is also often used; this is also measured in volts.

Resistance (R) 

is the variable that tells us the opposition to the flow of an electric current. Its unit of measurement in the International System is the ohm (Ω).

This same formula can be also be written in order to calculate for the voltage or the resistance: Triangle If you ever need help in remembering the different equations for Ohm's law and solving for each variable (V, I, R) you can use the triangle below. As you can see from the triangle and the equations above, voltage equals I times R, current (I) equals V over R, and resistance equals V over I.