So if generate an electric field or magnteic field, will it live for ever? because whenever you get rid of that field for example getting rid of electric field by discharging a capacitor, it will result in changing megntic field and that will result in changing electric field and that will keep on going on it own. Does it mean then that once introduced electric field or magnetic field will become immortal :)
Does it mean then that once introduced electric field or magnetic field will become immortal?
Not necessarily - as mentioned in a comment and in the praveen kr's answer, EM energy could be converted in other forms of energy - but, if it is not, it may get close to immortality. Take the light coming from stars that has been travelling for billions of years - that's pretty close to immortality and it is not dead yet.
So if generate an electric field or magnteic field, will it live for ever?
Generation of an electric field means the separation of charges; electrons in on direction and positrons on the other direction. Generation of a magnetic field means the alignment of the magnetic dipole moments of the involved subatomic particles. In both cases the fields are existing on the subatomic level, generation means only the collection to a macroscopic state. The macroscopic state doesn’t live forever, it will be destroyed again by sourrounding influences.
... getting rid of electric field ..., it will result in changing magnetic field and that will result in changing electric field and that will keep on going on it own. Does it mean then that once introduced electric field or magnetic field will become immortal...
To the above explained it has to be added that the separation of charges for the induction of a macroscopic field as well as for the induction of a macroscopic magnetic field energy is needed. During the destruction of these fields the contained additional energy gets emitted as electromagnetic radiation.
The emission happens in portions; Einstein called them quanta, later they were called photons. Photons are indivisible units during their lifespan. Photons get both an electric and a magnetic field component from the emitting particles and only in this commonness photons exist.
Once introduced will an electric and/or magnetic field live for ever?
Beside the macroscopic fields even the intrinsic fields of subatomic particles could vanish. This happens during the annihilation of electrons with positrons for example. Two or more photons with their combined EM fields convert the matter together with their intrinsic electric and intrinsic magnetic fields.