# Voltage

When charged electrons (current) are forced through a conducting loop by the pressure of an electrical circuit's power source, they can perform tasks like lighting a lamp.

In a short, voltage equals pressure and is expressed in volts (V). The name honours Alessandro Volta (1745–1827), an Italian physicist who developed the voltaic pile, the precursor of the modern household battery.

Early on, voltage was referred to as electromotive force (emf). This is the reason why the symbol E is used to denote voltage in equations like Ohm's Law.

Alternating or direct voltage is possible. The polarity of a direct voltage remains constant at all times. Periodically, the polarity changes in an alternating voltage. The frequency, which is expressed in hertz (one cycle per second), kilohertz, megahertz, gigahertz, or terahertz, is the total number of complete cycles per second. The potential difference between an electrochemical cell's terminals is an illustration of direct voltage. The terminals of a standard utility outlet are connected by an alternate voltage.

### Formula

Voltage is expressed mathematically as follows:
V = IR
V is the voltage in volts.
I equals current in amperes.
R is the resistance in ohms.

 SI unit of voltage Volt Symbol of voltage V, ΔV