Fundamental Formal

• electric field 

   

  E=F/Q 

  E is electric field in V/m or  N/c  

   (Volts per meter )or(newton / coulombs) 

  F is electric force in newton  

  Q is charge in coulombs  

   

   

  Electric charge Si unit Coulomb (C) symbol (a)  
• Charge 

  
  

  Q=IT = CV  

  Q= charge in coulomb (C) 

  I = Current in amperes (A) 

  T= time in seconds (S)

  C=capacitance in farad (F) 

  V=potential difference in voltage (V)  
• Resistivity and resistance 

  R =(P x L)/A  

  R = resistance (Ω) 

  P = Resistivity (ΩM) 

  I = length (m) 

  A = cross-sectional area ((csa) m²) 

   
• Ohm's law  

  V=I x R 

  V=voltage (v or u) 

  I=current (A) 

  R=  resistance (Ω) 
• emf 

  Emf = E x Q  

  emf = IR + Ir  

  E = energy in joules (J) 

  Q = charge in coulombs(C) 

  EMF = electromotive force (E) 

  I = current  

  R = resistances 
• Power 

  
  

  v² ÷ R = p  

  i × v = p   

  R × I² = p 
• Voltage  

  
  

  R × I = v  

  p ÷ i = v  

  √P × R = v

  
  

  V=voltage(V)

  R=resistance (Ω)

  P=power(W)
• Resistance 

  V ÷ I = R 

  V² ÷ p = R 

  P² ÷ I = R 
• Current 

   

   V ÷ R = I 

   P ÷ V = I 

  √P ÷ R = I