1.4 Standards of Electrical Measurements

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 change of charge : I=Q/T

• Ampere is the unit of current & Coulumb (C) is electrical charge

•1 coulomb ~6.24 x10^{18 electrons}

^{Voltage Standard}

• The volt (V) is the potential difference between two points on a conductor carrying a current of 1 A when the power dissipated between these points is 1 W. Volt (V) is the unit of electromotive force (emf) and potential difference.
  

• (1 Watt = 1 Joule/s)

• Volt = Watt / Ampere

• Watt = J/S = Power

• Joule = N/m = Work / Energy

• Newton = kg.m/s2

• 1 joule of work is consider done when 6.24 x 10^18 electrons (1 C ) are move through a potential difference of 1 V. One electron carries a charge of 1/(6.24 x 1018 ) 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 with electrons in orbit around the nucleus of an atom