8 Worth-Knowing Electrical Units of Measure


You might have ever heard Watt, Volt, or Ampere in your life. Those are electrical units of measure which are commonly used to express standard electrical units. Sometimes, they come with prefixes when the units are too large or too small.

If you dream of becoming a scientist or electrical engineer, it’s essential to understand common unit of electrical measurement along with their functions. The following units are based on System International (SI) metric system.

Standard Electrical Units of Measure
Standard Electrical Units of Measure

Volt for Voltage

Voltage, which is often known as potential difference, is defined as the pressure that causes electrons movement in an electrical conductor. It can also be described as the force which pushes the charges. Voltage can cause a current by moving charges.

In some circumstances, voltage is often called as electromotive force (EMF). The unit of voltage is volt and it is taken from the name of Alessandro Volta. This unit is symbolized with an uppercase V because it is derived from the name of a person. But in some circumstances, voltage is symbolized with an uppercase E.

Voltage can be measured with some specific tools known as the voltmeter as well as oscilloscope. When using voltmeter, the voltage is measured between two points. It allows you to set the mode to DC or AC. The DC mode can be used for a battery or DC circuit while the AC mode can work for power socket.

Ampere for Current

Another standard unit of electrical measurement is Ampere. This unit is used to express electric current, the rate of electric charge flow that past a point. Ampere is symbolized by an uppercase A, or often shortened to amp. This unit is named after Andre-Marie Ampere, the French physicist and mathematician.

This one of electrical units of measure is often determined by reading the electromagnetic force among two conductors which carry the currents. Another measurement can be conducted using electric charge, in which force between two charged metal plates can be defined.

According to the SI system, charge that is delivered by an ampere in 1 second is known as the coulomb. It can be written as: 1A = 1C/s. In practice, the standard ampere is maintained through Ohm’s law or Kirchhoff’s laws.

Ohm for Resistance

Ohm is one of SI’s electrical units of measure used for electrical resistance. This unit is named after Georg Simon Ohm, a German physicist. It is often symbolized with W (omega).

When one volt is applied in a conductor then results in one ampere of current, the emerging electric resistant between 2 points is known as one Ohm. Given that, one Ohm can be written as 1 ohm = volt / ampere.

A multimeter is a tool which can be used to measure electrical resistance in ohms aside from ohmmeter. There are micro-ohmmeters as well as megohmmeter to measure different level of resistance.

Siemens for Conductance

Siemens, often symbolized by an uppercase S or an uppercase G, is a unit to express electric conductance. This unit of measurement is also used to express electric admittance and susceptance in SI units. The conductance, admittance, and susceptance are the reciprocals of resistance, impedance, and reactance.

As with other standard unit, siemens is named after Ernst Werner von Siemens. There is an alternative name to siemens, which is the mho. Electric conductance can be defined as G= 1/R or G= I/V. The V refers to voltage while the I refers to electric current through the object.

Meanwhile, the unit Siemens can be defined as [S] = [A / V]. It means if a device has a conductance of one siemens, the electric current will increase by 1 ampere when the potential difference increases by one volt.

Farad for Capacitance

Farad is among derived electrical units of measure for electrical capacitance. Capacitance is the ability of a device to store an electrical charge. The unit is named after Michael Faraday, the English physicist. Farad is symbolized by an uppercase F.

One farad can be described as the capacitance of a body in which there is a potential difference of one volt when charged with one coulomb. Or, one farad can be defined as the capacitance which keeps one-coulomb charge across one volt of potential difference.

The definition above can be written as F = C / V. Capacitance is linear with charge and potential difference. It means, when the potential difference is halved, then the charges will be halved

Coulomb for Charge

According to International System of Units, coulomb is used for electrical units of charge which is symbolized by a capital C. Charles-Augustin de Coulomb where the unit’s name came from.

Coulomb can be described as one charge (Q or q) which is transported by 1 ampere of current in 1 second or 1 C = 1 A x 1 s. It is also described as the amount of excess charge on an electric capacitor of one farad that is charged to one volt of potential difference. It can be written as 1 C = 1 F x 1 V.

In everyday practices, a few micro-coulombs can be found from the charges of static electricity resulted from rubbing materials together. Meanwhile, a lightning bolts can result around 15 C.

Henry for Inductance

Henry, often symbolized with an uppercase H, is one of electricity measurement units of electrical inductance. The unit is called after an American scientist named Joseph Henry. He discovered electromagnetic induction, interestingly at about the same time as Michael Faraday.

Inductance can be defined as one henry when electric current at one ampere per second produces a potential difference of one volt. This unit is derived from four base units including kg, m, s, and A.

Hertz for Frequency

Hertz (Hz) is one of electrical units of measure of frequency, which means how often something occurs. One hertz of frequency is when something occurs once in one second. Heinrich Rudolf Hertz a German physicist whose name is used to name this unit.

Hertz is often found in everyday life, such as:

  • Computer processors
  • Electronics
  • Amateur radio