July 29, 2008

Voltage, Current and Resistance

Basic Electrical Quantities

In electronics we are dealing with voltage, current and resistance of a circuit. In this lesson we will discuss the characteristics of each electrical quantities and how each quantity relates with the other.

Voltage is also called as 'potential difference' or 'electrical pressure' or 'electromotive force' that exists between two points in a circuit. As an electrical pressure, the voltage forces the electrons to move from one point to another. Voltage is measured in terms of volts. The unit volt is named after an Italian scientist Count Alessandro Volta, the inventor of the first battery, the Voltaic Pile.

Voltage: E
Volt: V


Electric current is the amount or the number of electrons moving along a conductor or a circuit at a given time. Why did electrons move? Electrons move because of the electromotive force or the voltage. Current or the intensity of current flow is measured in ampere. Ampere is named after the French Physicist and Mathematician, Andre Marie Ampere.

Intensity of current flow or current: I
Ampere: A or Amps


Resistance is anything which opposes or limits the flow of electrons in a circuit. Resistance is measured in terms of ohms. The unit ohm is named after the German Physicist Georg Simon Ohm. He formulates the Ohm's Law - the relationship among voltage, current and resistance.

Resistance: R
Ohm: Ω

We can relate the characteristics of the three electrical quantities with a person pushing a cabinet. The force exerted by the person to make the cabinet move from one point to another is the voltage, when the cabinet moves from one point to another, it's like the current or the electrons flowing along a conductor or electrical path, the friction offered by the flooring signifies resistance, while the cabinet symbolizes the electron.