UNITS OF MEASUREMENT IN ELECTRICAL ENGINEERING
E.M.F Volt 108 Power in direct current circuits
Current Amp 10-1 Volts V = V x 108 electrostatic units
Resistance Ohm 109 Coulombs Q = Q x 10-1
Work Joule 107 Specific resistance : V = R x 1
Capacity Micro Farad 10-15 Work Done = V x 108 x Q x 101
. Farad 10-2 =VQ x 107 ergs
Power Kilowatt 1010 =VQ x 107 ergs = W Joules
. Watt 10 = VIt Joules
Energy Kilowatt Hour 36 x 1012 .

ELECTRICAL UNITS - THEIR EQUIVALENTS AND FORMULAE
1.H.P = 746 watts = 0.746 Kw = 33,000 ft.lbs per minute = 1,014 metric HP
1 B.O.T -
 1000 Watts hour or 1 K.W.hour
Current =
 Watts + Volts(for DC)
K.V.A =
 (Volts x AMPS) + 1000
Power Factor =
 ratio of true power / apparent powers
=
  K.W + K.V.A
Single Phase Motor Amperes =
 H.P x 746 / Efficiency x Volts x Power Factor
Two -  Phase Motor Amperes =
  H.P x 746 / Efficiency x Volts x Power Factor x 2
Three - Phase Motor Amperes =
 H.P x 746 / Efficiency x Volts x Power Factor x 1.73
Torque(ft.lb~=
 (H.P x 33,000) + ( R.P.M) x 2
1 Electrical unit =
 1 Kilowatt Hour
1 Kilowatt(K.W) =
 738 Ft.lbs.per sec
=
 102 M.Kg.per sec
=
 1.341 horse power
=
 1.360 metric horse power
1 Kilowatt (K.W.H)=
 3.413 B.Th.U
=
  860 Calories
1 Calorie =
 3.088 foot pounds
=
 3.968 B.Th.U
1 B.Th.U =
 778.3 ft lb
107.6 M.Kg
0.2520 calories
1 Foot pound (ft.lb) =
 0.1383 M.Kg
Mechanical equivalent of heat is 4.18 x 101 ergs / calories or 4.18 joules /cal
Heat developed in conductor =
 0.239 I2 Rt calories
Heat developed in Water or liquid heater =
 M grammes x sp.heat x T C x I2 Rt/4.18
Power in Alternating circuit
Inductive reactance =
 2¶fl hms
Capacitive reactance =
 (1 / 2¶fc) Ohms; V = Voltage Applied
Impedence =
 [R2 + ( 2¶fl - 1/2¶fl)2]½ = z
1 = current;L = inductance; R = resistance;f = frequency of supply; C = capacitance
Current ; V/= [ R2 + (2¶fl - 1/2¶fc)2]½ = V/Z
if 2 fL = 1/2 tc there is resonance and 1 = V/R
Power in single phase A.C circuit = volts x amps x power factor
In a 3 phase circuit power (watts) = [(3)½ x Volts x amps x power factor]

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