• Matter possesses a property called electric charge and there are only two kinds of electric charges: positive charge and negative charge.
• The charge carried by a proton or an electron is the ultimate natural unit of charge whose magnitude (e) is

e = 1.602 × 10^-19 C

• Materials which permit the flow of charge through them are called conductors of electric current. On the other hand, materials like the nylon cord that do not allow the flow of electric current through them are called insulators.
• Electrically neutral objects can be electrified by rubbing (friction), by sharing (conduction) and by induction. By rubbing, objects are charged oppositely; by touching or by sharing, objects are charged similarly; and by induction bodies are charged oppositely.
• The interaction between any two charges is governed by the basic laws of electrostatics, which are stated as, "like charges repel each other and unlike charges attract each other".
• The force of interaction of two electrostatic point charges in vacuum is directly proportional to the product of the two charges and inversely proportional to the square of their separation.
• The magnitude of the force between two point charges q₁ and q₂ which are at a distance r apart, is given by Coulomb law as

• If a force of electrical origin is exerted on the test charge, then an electric field exists at the point.
• The magnitude of the electric field strength due to charge Q at a point a distance r from the charge is given by

• The direction of the electric field strength is conventionally determined to be towards charge Q if it is negative charge and away from Q if it is positive charge.
• Electric field can be visualized as consisting of imaginary lines called electric lines of force. Each line corresponds to the path that a positive test charge would take if it is placed in the field on that line.
• The potential difference between two points in a uniform electric field at a distance d is

V_AB = Ed

• The electric field strength between any two points at a distance ∆r and having p.d ∆V is

• The expression ΔV /Δr is called potential gradient.
• A capacitor is a device used to store electrical charge and energy. During charging a capacitor, the charge stored in the capacitor is directly proportional to the potential difference developing between the plates. Therefore, we can define a proportionality constant as

• Capacitance is defined as the ability of a capacitor to store electrical charge and energy.
• When several capacitors are connected in series, the equival9ent capacitance is

• When several capacitors are connected in parallel, the equivalent capacitance is

C_eq = C₁ + C₂ +…