Introduction to E.M.

Quantization of charge

Electric charges always come in integral multiples of charge on an electron/proton. However quarks(building blocks of electrons) have charges n(e/3) where n=1, 2. because they have not been isolated they are counted as the quantized charge.

Coloumbs law

            Coloumbs law into its simplest form can be written as:

                       

                        F=(Qq)ř/r²

            The force is always along the line of separation between the charges

Energy of a system of charges

The energy of a system of charges is defined as the amount of work done in bringing the charges into the required configuration without acceleration.

We know that work done

            W=F.ds

Let two charges Q and q be brought from infinity to a separation r without acceleration.

Work done is:

            W=∫(Qq)/r²(-dr)

The negative sign indicates that there is a decrement in the distance

Solving we get

            U=W=Qq/r

Generalizing

            U=(1/2)∑∑(Qq)/r

Flux

Flux of an electric field is the amount of electric field lines passing through a

given surface area.

            Φ=∫E.da