Quantities and Units use in Electrical and Electronicstopjankari.com

Quantities and Units use in Electrical and Electronics

Quantities and Units use in Electrical and Electronics.

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Volt ( V or E):-

Volt is the electrical unit of voltage. Measuring unit of volt is represented by a letter V or E.

One volt is the energy of 1 joule that is consumed when electric charge of 1 coulomb flows in the circuit.
1V = 1J / 1C
Ampere ( A):-


Ampere is the electrical unit of electric current. Measuring unit of ampere is represented by a letter I or i. I

measures the amount of electric charge that flows in an electrical circuit per 1 second.
1A = 1C / 1s
Ohm(Ω ):-

Ohm is the electrical unit of resistance. Measuring unit of Ohm is symbolized by a latter R or a Greek letter Ω.

For AC the resistance is said Impedance and is represented by a letter Z.
1Ω = 1V / 1A

Z [Ω] =√ (R2 +X2 )
Watt (W):-

Watt is the electrical unit of electric power. It measures the rate of consumed energy.

1W = 1J / 1s
1W = 1V • 1A
Decibel miliwatt (dBm):-

Decibel-milliwatt or dBm is a unit of electric power, measured with logarithmic scale referenced to 1mW.
10dBm = 10 •log10 (10mW / 1mW)
Decibel-watt (dBW):-

Decibel-watt or dBW is a unit of electric power, measured with logarithmic scale referenced to 1W.
10dBW = 10 • log10(10W / 1W)
Farad (F):-

Farad is the unit of capacitance. Measuring unit is represented by a letter C. It represents the amount of electric charge in coulombs that is stored per 1 volt.
1F = 1C / 1V
Henry (H):-

Henry is the unit of inductance. Measuring unit symbol is represented by a letter H or L.
1H = 1Wb / 1A
Siemens (S):-

Siemens is the unit of conductance, which is the opposite of resistance. The measuring unit of  conductance is represented by a letter G
1S = 1 / 1Ω=1Mho


Coulamb (C):-


Coulomb is the unit of electric charge.
1C = 6.238792×1018 electron charges
Ampere-hour(Ah):-

Ampere-hour is a unit of electric charge. One ampere-hour is the electric charge that flow in electrical circuit, when a current of 1 ampere is applied for 1 hour.
1Ah = 1A • 1hour

One ampere-hour is equal to 3600 coulombs.

1Ah=3600 C.
Tesla(T):-

Tesla is the unit of magnetic field.
1T = 1Wb / 1m2
Weber (Wb):-

Weber is the unit of magnetic flux.
1Wb = 1V • 1s
Joule (J):-

Joule is the unit of energy.
1J = 1 kg • 1(m / s)2
Kilowatt-hour (kWh):-

Kilowatt-hour is a unit of energy.
1kWh = 1kW • 1h = 1000W • 1h
Kilovolt-amps(kVA):-

Kilovolt-amps is a unit of apparent power.
1kVA = 1kV • 1A = 1000 • 1V • 1A.    
Hertz (Hz):-

Hertz is the unit of frequency. It measures the number of cycles per second.
1 Hz = 1 cycles / s
Voltampere-reactive(Var):-

Var is the unit of Reactive power and its measuring unit symbol is represented by a letter Q. In inductor or capacitor how much magnetic or electric field made by 1Ax1V is called the unit of reactive power.

1Var=1V.1A
Q= V•I •sinθ; This can be positive for inductance and negative for capacitance.
Ohm-meter (Ω·m):-

Ohm-meter is the unit of electrical Resistivity. Resistivity is symbolized by Greek small letter Rho ​​​​​​“ρ”.
1 Ω•m=1Ω•1m
• Siemens per meter (S/m)

Siemens per meter is the unit of Conductivity. Measuring unit of conductivity is represented by Greek small letter sigma “σ”
1S/m=1siemence/1meter
• Volts per meter (V/m) ;-

Volts per meter is the unit of Electric Field. Measuring unit of Electric Field is symbolized by a letter E.
1V/m=1Volt/1meter
• Newton per coulomb (N/C) :-

Newton per coulomb is the unit of Electric field. The unit of measuring of Electric Field is symbolized by a letter “E”.
1N/C=1Newton/1Coulomb
• Volt-meter (V·m) :-

Volt-meter is the unit of Electric Flux. Measuring unit of Electric Flux is symbolized by “Φe”.
 1Vm=1Volt•1meter
The relationship between quantities can be written using words or symbols (letters), but symbols are normally used because they are much shorter.  
For example V is used for voltage, I for current and R for resistance: As a word Equation:- V= current × resistance The  same equation using Symbols:- V=I×R