Electric Field and Potential Notes & Topics for Electrical Engineering

• Where, n = Number of point charges, Q_i = Charge of each point charge, V_i = Potential at location Q_i due to all the other charges except that of charge Q_j itself.
• Due to continuous charge distribution, the energy density is obtained by

• Boundary Conditions for Perfect Dielectric Materials

• The two dielectrics having permittivities ε₁ and ε₂.
• Here, tangential component of electric field is continuous E_t1 = E_t2
• The normal component of electric flux density is continuous D_N1 = D_N2
• D₂ and E₂ can be given by

• Electric flux density at point 2

• Electric field intensify at point 1

• Electric current in terms of current density

• where J is current density:

• Convection currents do not involve conductors and do not obey the Ohm’s law, convection current density is J = ρ_Vu; where, u is velocity and ρ_v are volume charge density.
• Conduction currents involve conductors and obey Ohm’s law conduction current density is J = σ E; where, σ is conductivity and E is electric field intensity,
• For perfect conductor: 
• The resistance of a conductor is:

• Dipole moment p of the electric dipole can be given as p = Q d; where d is the distance vector –Q to +Q.
• Polarisation vector p is the net dipole moment per unit volume of the dielectric.

• If a dielectric has in-built dipole ten it is known as a polar dielectric.
• If in a dielectric dipole is resulted as the effect of external electric field, dielectric is known as a non-polar dielectric.
• Polarisation surface charge density:

• Polarisation volume charge density:

• Hence, the effect of dielectric on electric field is to increase the flux density by an amount p.
• p is proportional to the applied electric field E

where,  = Electric susceptibility

All the Best.