Electrostatics

Electric charge: Electric charges are of two types: positive and negative. Like charges repel each other while opposite charges attract each other. Electrostatic induction: If in the presence of a charged body, an insulated conductor has like charges at one end and unlike charges at the other end then this is called electrostatic induction. Electroscope: It is an instrument used for detecting and testing the nature of charge on a body. Coulomb's law: The force of attraction or repulsion between two charged bodies is directly proportional to the product of the quantity of charges on them and inversely proportional to the square of the distance between them. This is called coulomb's law. Electric field: The electric field of a charge is a region of space surrounding it, in which a charge can feel its electrostatic effect in the form of a force. Electric lines of forces: The direction of electric intensity in an electric field can also be indicated by drawing lines. These lines are known as electric lines of forces. They are imaginary lines. Electric potential: The potential at any point in the field is defined as the potential energy of a unit positive charge placed at that point which is equal to the amount of work done in bringing a unit positive charge from infinity to that point If W is the amount of work done in bringing a positive test charge +q from infinity to a certain point in the field, the potential V at this point would be V=W/q Capacitance: Capacitance is the ability of a capacitor to store charge. Capacitance of a conductor is equal to the amount of charge which raises the potential of the conductor by one volt. The unit of capacitance is farad. Combinations of capacitors: i)                   Parallel Combination In this method left plates of all capacitors are connected to one point and right one to other point. ii)                 Series Combination In this combination capacitors are connected plate to plate that is left plate of a capacitor is connected with right plate of other capacitor and so on. Types of capacitors: i)                   Fixed Capacitors If the capacitors are such that its plates are immovable, it is known as a fixed capacitor. Its value does not change. Paper capacitor, mica capacitor etc ii)                 Variable Capacitors If in a parallel plate capacitor some arrangement is made so that the area of the plates facing each other can be charged then it is called variable capacitor.