2.2 Electric Fields, Voltages and Energies

• The electrical force F between two charged particles with q1 and q2 units of electronic charge separated by a distance r is given by Coulomb's law: F = kc.(q1.q2)/r^2 
• Coulomb law constant: kc = 8.988 x 10^9 m per farad

Chp 2 Current Flow & Capacitance

• Current flow (I) = q.n.vd.A 
• vd is the velocity component directed along the metal bar / drift velocity
• q is the charge on electrons (-1.6 x 10-19 c)   
• n is number of electrons per unit volume
• A is area
• To describe the current flow in a cross section of area A, we define the current density:
• J = I / A = n.e.vd