Principles of Electrical Science - 202

Principles of Electrical Science - 202

1. Principles of Electricity

   • Electron Theory
     • Protons are positively charged
     • Electrons are negatively charged
     • Electrical neutral atoms
       • Protons are equal to the number of Electrons
     • Random free electron movement
       • Battery provides a source of electromotive force (EMF).
       • The resultant electron flow around the circuit is called an Electric Current.
   • Sources of an EMF
     • Electromagnetic Induction
     • Electrochemistry
     • Photoelectric Effect
     • Thermoelectric Effect
     • Piezoelectric Effect
   • Effects of an Electric Current
     • Thermal
     • Chemical
     • Magnetic

2. Ohms Law

   • V = I x R
   • I = V/R
   • R = V/I

3. Useful Formulae

   • Voltage = I x R = P/I = square root P x R
   • Current = V/R = P/V = square root P/R
   • Resistance = V/I = V squared/P = P/I squared
   • Power = V x I = I squared x R = V squared/R
   • In series: Rt = R1 + R2 + R3 etc
     • Resistors
       • In parallel: 1/Rt = 1/R1 + 1/R2 + 1/R3
   • Kirchhoffs Laws
     • Voltage: VT = V1 + V2 + V3 etc in a series circuit
     • Current: IT = I1 + I2 + I3 etc in a parallel circuit
   • Capacitors
     • In parallel: Ct = C1 + C2 + C3 etc
     • In series: 1/Ct = 1/C1 + 1/C2 + 1/C3 etc
   • Induced EMF
     • E = B x l x v
     • E = -L x (I2 - I1)/t
   • Force on a conductor
     • F = B x I x l Newtons
   • Efficiency
     • Efficiency = Output Power /Input Power
   • Power Factor
     • p.f. = R/Z
     • p.f. = P/VA