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ENGINEERING FORMULA

ELECTRICAL

DIRECT CURRENT(DC)

I = current(amps.), V = voltage(volts), R = resistance(ohms), P = power(watts)

  • CURRENT:
I = V/R or I = P/V    

  • VOLTAGE:
V= P/I or V = IR  

  • POWER:
I2R or VI       

  • RESISTANCE:
R = V/I   

ALTERNATING CURRENT(AC):

Il = line current(amps.), Ip = phase current(amps.), Vp = phase voltage(volts), Vl = line voltage(volts), Z = impedance(ohms), P = power(watts), f = power factor(angle), VA = volt ampers

  • CURRENT(single phase):
I = P/(Vp cos(f)

    
  • CURRENT(3 phase):
I = P/√3(Vl cos(f)) or I = P/3(Vp cos(f))

  • POWER(single phase):
P = (VpIp cos(f))

  • POWER(3 phase):
P = √3(VlIl cos(f)) or P = 3(VpIp cos(f))
Last updated 1-13-09