MOTORS AND GENERATORS PHYSICS QUANTITIES You need to have a good working knowledge and understanding of the physical quantities their symbols and units listed below. Symbol Physical Quantity SI unit Unit Vector / (non SI) direction /sign angle rad degrees yes 1 revolution = 360o = 2 rad area (direction given by m2 yes A outward pointing normal) length of conductor m metres no L electric current A ampere yes I, i electric charge (+) (-) C coulomb yes Q, q |e| = 1.60210-19 C potential difference V volts yes V emf voltage due to a source emf – of electrical energy electric field N.C-1 yes V.m-1 R electrical resistance ohm no permittivity of free space N.m2.C-2 no o = 8.551-12 C2.N-1.m-2 = 9.0109 N.m2.C-2 k force N newton yes electric and magnetic kinetic energy J joule no K KE EK work J yes W potential energy J yes PE U EP power W watts no P magnetic field strength T tesla yes magnetic flux density T.m2 yes permeability of free space T.m.A-1 no o = 410-7 T.m.A-1 mass kg g no m = 9.1110-31 kg me number of turns of wire in a no n N coil time interval s second min no t, t hour day torque N.m yes velocity m.s-1 km.h-1 yes
MOTORS AND GENERATORS PHYSICS QUANTITIES You need to have a good working knowledge and understanding of the physical quantities their symbols and units listed below. Symbol Physical Quantity SI unit Unit (non SI) Vector / direction /sign angle 1 revolution = 360o = 2 rad rad degrees yes A area (direction given by outward pointing normal) m2 yes L length of conductor m metres no I, i electric current A ampere yes Q, q electric charge (+) (-) |e| = 1.60210-19 C C coulomb yes V potential difference V volts yes emf emf – voltage due to a source of electrical energy electric field N.C-1 V.m-1 yes R electrical resistance ohm no permittivity of free space o = 8.551-12 C2.N-1.m-2 k = 9.0109 N.m2.C-2 N.m2.C-2 no force electric and magnetic N newton yes K KE EK kinetic energy J joule no W work J yes PE U EP potential energy J yes P power W watts no magnetic field strength T tesla yes magnetic flux density T.m2 yes permeability of free space o = 410-7 T.m.A-1 T.m.A-1 no m mass me = 9.1110-31 kg kg g no n N number of turns of wire in a coil no t, t time interval s second min hour day no torque N.m yes velocity m.s-1 km.h-1 yes