# Weights and Measures Act 1985, Part VII: Measurement of Electricity

Extent: E+W+S+N.I.

1.
(a) AMPERE
for which the symbol “A” is used, is the SI unit of electric current, defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10-19 when expressed in the unit C, which is equal to A s, where the second is defined by taking the fixed numerical value of the caesium frequency ΔvCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s-1.
(b) OHM
is the electric resistance between two points of a conductor when a constant potential difference of 1 volt, applied between the two points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.
(c) VOLT
is the difference of electric potential between two points of a conducting wire carrying a constant current of 1 ampere when the power dissipated between these points is equal to 1 watt.
(d) WATT
is the power which in one second gives rise to energy of 1 joule , where the second has the meaning given in the definition of “AMPERE”.
2.
Kilowatt
= 1000 watts.
Megawatt
= one million watts.

---
Source: https://www.legislation.gov.uk/ukpga/1985/72/schedule/1/part/VII (the official version)
Page: https://openlegislation.uk/weights-and-measures-act-1985/schedule-1/part-VII
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.