1.4 Standards of Electrical Measurements

standards of electrical measurement

CURRENT STANDARD

Current is the quantity of electricity charge (Q) that passes a given point in a conductor
During a time of 1 second or the time rate of the change of charge (I=Qt).
Unit of current Ampere.
Unit of electrical charge Coulumb.
1 Coulumb 6.24x10^18 electrons.

VOLTAGE STANDARD

The volt is a potential difference between two points on a conductor carrying a current of 1A when the power dissipated between these points is 1W.
Volt (V) is the of electromotive force (emf) and potential difference.
1 Joule of work is consider done when 6.24x10^18 electrons 1C are move through a potential difference of 1Volt
1 electron carries a charge of 1/(6.24x10^18 C. When only 1 electron moved through 1V, the energy known as electron volt (eV).
eV is used in the case of very small energy level associated.

RESISTANCE STANDARD

Ohm is defined as the resistance which permits a current flow of 1A when a potential difference of 1Volts is applied to the resistance.
Units of resistance ohm,

INDUCTANCE STANDARD

Unit of inductance Henry(H).
The inductance of a circuit is 1 Henry, when an emf of 1 volt is induced by the current changing at the rate of 1A/s.
Unit of magnetic flux , Weber(Wb)
Unit of magnetic flux density, Tesla (T).

1H=1Wb/1A

1Wb=1V x 1s

L=(4π ^2 x 10^-7N^2r^2) / l

N; number of wire turn

R; solenoid radius in meter

L; length of solenoid in meter

RESISTANCE STANDARD

Unit of capacitance farad (F).
The farad is the capacitance of a capacitor that contains of 1C when the potential difference between its terminal is 1 volt.

1Farad = 1 Coulomb / 1volt

where,

1Q = 1Ampere x 1s

Note; Q is refer to the charge carried by one electron.

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