International System of Units (SI) Metric System
Electrical measuring units can be obtained using Ohm’s Law and the International System of Units (SI) Metric System.
Watts and kilowatts measure electricity
Electric power is measured in Watts, named after James Watt, who developed the steam engine and power in watts which is equal to 1 ampere at 1 volt of pressure.
One watt of power is inadequate. Some devices require only a few Watts to operate, while others require much more. Small devices power consumption is often measured in Watts, while bigger devices power consumption is typically measured in kilowatts (kW), or 1,000 Watts.
Megawatts (MW) and gigawatts (GW) measure electricity generation capacity (GW). 1 GW is 1,000 MW.
Electricity consumption is measured in Watthours over time
A Watthour (Wh) is the energy of one Watt provided to or removed from an electric circuit over the duration of one hour. The amount of electricity generated by a power plant or consumed by an electric utility customer is normally measured in kilowatt-hours (kWh). One kWh is one kilowatt-hour generated or consumed.
EX: if use a 40-Watt (0.04 kW) light bulb for five hours, it will have used 200 Wh, or 0.2 kWh of electricity.
Meters are used by utility companies to measure and track how much electricity is used
Meters on the outside of a possessions, near where the power line comes in, are usually used by electric companies to measure how much electricity uses. In the past, all electricity meters were mechanical devices that a utility worker had to read by hand. Automatic readers became available recently. These mechanical meters send an electronic signal to the power company every so often to tell them how much electricity they are using. Now, many utilities use electronic smart meters, which provide wireless access to the data on how much electricity is being used. This makes it possible to measure how much electricity is being used in real time. Some smart meters can even track how much electricity each device uses and let the power utility or the customer control electricity use remotely
The electrical parameters listed below, including the unit of measurement and their relationship to other parameters.
- Voltage
- Current
- Resistance
- Conductance
- Power
- Inductance
- Capacitance
- Charge
- Impedance
- Frequency
Electrical Standard Units
Electrical units of measurement are based on the International (metric) System, generally known as the SI System. The following are electrical measurement units:
1). Voltage
The pressure or force that causes electrons to flow in a conductor is referred to as voltage, electromotive force (emf), or potential difference. Voltage is frequently represented with a capital E in electrical calculations and equations, but with a capital V on schematic diagrams.
V = I R
2). Current
The flow of free electrons via a conductor is defined as electron current, or amperage. In electrical calculations, current is represented by a capital I, in schematic diagrams, amps or amperage is commonly represented by a capital A. (amps).
I = V/R
3). Resistance
The opposition to current flow is referred to as resistance. The degree of resistance to current flow created by a material is determined by the number of available free electrons and the types of difficulties experienced by the electrons as they pass through the material. It is denoted by R.
R = V/I
4). Conductance
Conductance, often known as electrical conductance, is the ability of a substance to conduct electricity. Conductance is a measure of how easily electrical current, or charge flow, may move through a substance. Conductance is the inverse of electrical resistance, denoted as G or ℧.
G = 1/R
5). Power
An electric power is the rate at which work is done in an electrical circuit. In other terms, electric power is defined as the rate at which energy is transferred. It is denoted by P or W.Watt is the SI unit of power.
P = V × I (or) I2 × R
6). Inductance
The amount of magnetic energy that may be held in an inductor is referred to as the inductance, and it is defined as the ratio of the magnetic flux to the current. The SI unit is Henry and denoted by H or L. Another way to express the inductance L of a conductor that is carrying a current I is as follows:
L = ø/I
7). Capacitance
Capacitance is a method to measure how much an object can store an electric charge. This capacitance value also depends on the dielectric constant of the material used to separate the two parallel plates. The Farad is the SI unit used to measure capacitance (F) and denoted by C.
C = Q/V
8). Charge
Electric charge is a fundamental physical feature of matter. Electric charge can be positive or negative. Matter repels matter of the same charge and attracts matter of the opposite charge. Coulomb is the unit of electric charge and denoted by Q.
Q = C X V
9). Impedance
Impedance, denoted by the symbol Z, is a measurement of the resistance to electrical flow. Ohms are used to measure resistance.
In direct current (DC) systems, impedance and resistance are defined as the voltage across an element divided by the current
R = V/I
In alternating current (AC) systems, impedance can be determined as,
Z2 = R2 + X2
10). Frequency
Frequency is a measurement of the rate of that oscillation and is expressed in terms of the number of changes per second. The SI unit of frequency is Hertz and denoted as Hz.
f = 1/T
| Electrical Parameters | Symbol | Unit | Formula |
|---|---|---|---|
| Voltage | V | Volt | V = I × R |
| Current | I | Ampere | I = V / R |
| Resistance | R or Ω | Ohm | R = V / I |
| Conductance | G or ℧ | Siemen/mho | G = 1 / R |
| Power | P or W | Watts | P = V × I or I2 × R |
| Inductance | H or L | Henry | L=ø/I |
| Capacitance | C | Farad | C = Q/V |
| Charge | Q | Coulomb | Q= C x V |
| Impedance | Z | Ohm | Z2 = R2 + X2(AC) R=V/I (DC) |
| Frequency | Hz | Hertz | f=1/T |
Sub-multiples and multiples
Between the maximum and minimum values of a standard electrical unit, there is a wide range of values experienced in electrical and electronic engineering. Resistance, for example, can be less than 0.01Ω or greater than 1,000,000Ω.
By employing multiples and submultiples of the standard unit, it may describe the position of the decimal point without having to write too many zeros. The following table contains their terms and power values.
| Term | Symbol | Multiplier | Power Value |
|---|---|---|---|
| Tera | T | 1000000000000 | 1012 |
| Giga | G | 1000000000 | 109 |
| Mega | M | 1000000 | 106 |
| Kilo | K | 1000 | 103 |
| None | None | 1 | 100 |
| Centi | cm | 1/100 | 10-2 |
| Milli | mm | 1/1000 | 10-3 |
| Micro | µ | 1/1000000 | 10-6 |
| Nano | n | 1/1000000000 | 10-9 |
| Pico | p | 1/1000000000000 | 10-12 |
To convert from one prefix to another, either multiply or divide by the difference between the two values.
Additional Electricity Units
Other units, in addition to the conventional units, are used to express values and quantities. The following are:
Wh –Watt-Hour:The Watt-Hour is the quantity of electrical energy utilised by an electric circuit over a specific time period. A typical electric bulb, for instance, consumes 100 watts per hour.
dB – Decibel: A Decibel is equal to one-tenth of a Bel (symbol B). It represents an increase in voltage, power, or current.
θ – Phase Angle: It is the difference (in degrees) between the waveforms of voltage and current that have the same time period. It is a time difference that depends on the component of the circuit. Its value may be “leading” or “lagging.” Likewise, it is measured in radians.
ω – Angular Frequency:Angular Frequency is used to express the phase relationship between two waveforms.
Ï„- Constant Time:The Time Constant is an impedance circuit characteristic. It is the amount of time required for the output to reach 63.7% of its minimum or maximum value when step response input is applied. It is a measure of reaction time.
