 # Electric Charges and Fields

## •    Electrostatics is the branch of physics that deals with stationary electric charges that means electric charges at rest. •    An electric charge is a fundamental characteristic property of elementary particles of matter which can explain certain forces of interaction and some type of interaction energies. The two types of charges are: positive charge and negative charge. •    A body acquires positive charge due to transference of electrons away from it and a body acquires negative charge due to the transference of electrons to it from another body. •     A simple apparatus to detect charge on a body is the gold-leaf electroscope. •    Electrical conductors are the materials that allow the electric current to pass through them. •    Electrical insulators are the materials that do not allow the electric current to pass through them. •    Charging of a body can be done in two ways: induction or conduction. •    Electric charge has three basic properties: quantisation, additivity and conservation. Quantisation means total charge of body is always integral multiple of e. •    The colulomb’s law defines the force between two bodies when they are placed near each other. It states that force experienced by two charges is directly proportional to their product and inversely proportional to square of the distance between them. •     Force on any charge due to number of other charges can be calculated using Superposition principle. •    The force experienced by charges is due to their Electric field. Electric field is the area around a charge in which its electrical influence can be experienced. •    Electric field lines are used to represent electric field around the electric charge. •    Electric Flux is the number of electric lines of force passing through a surface in an electric field. •    A pair of equal and opposite point charges, q and –q separated by some distance forms an electric dipole. •    Electric dipole moment is defined as the product of the magnitude of either charge and distance between them. The field due to dipole is the space around the dipole in which the electric effect of the dipole can be experienced. On axial and equatorial line of an electric dipole, the field is different. In uniform electric field, electric dipole experiences a torque. •    The electric field due to uniformly charged bodies can be found by using Gauss’s Law. Gauss’s Law states that, total electric flux phi( ), through a closed surface (S) is equal to one upon epsilon knot

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