IIT JEE , AIEEE Forum - Physics , Modern Physics

anpm_dev

what is forbidden energ ygap

risin

It is the energy gap between the valence band and the conductance band like in insulators it is huge(>3ev).

ankiani

forbidden energy gap(FEG) is the gap between the electrons of conduction band and valence electron band.It is negligible in conductors....for insulators it is 6-7ev so they can't conduct electricity. In case of semiconductor it varies depending on temprature

drritu

actually it is tat energy required to exite electron to make them conducting
der is not as such valence or conduction levels in the atom

sathya_crazyteen

actually forbidden energy gap is the energy barrier that exists between the valence band and conduction band of a material (not necessarily a metal) .energy bands are formed in case of solids dur to the overlapping of the energy levels in atoms which lie very close to one another .valence band is one which has got the outermost electrons and it cannot b empty.on teh other hand the conduction band is one to which electrons from the valence band move after they sare supplied with the energy greaterr thatn or equal to that of the forbidden energy gap..

hope u got it

rate me if its useful :)

TheVisualiser

To put it simply (might not be 100% accurate but close too it, and hopefully easy to understand). As you might know when two waves meet, and the crest of one wave (the high point) meets exactly with the trough of another (the low point), the wave cancels.

Now picture the classic view of an atom, with the electron "orbiting" the nucleus, you might think of the electron as one single point, like a particle. In reality the electron is a wave going around the nucleus. Now i want you too picture a wave from side on, now extend that around a point, so it's circling the nucleus. Now i want you to imagen the wave catching up with it's tail, depending on the frequency and stuff of the wave, it might cancel at different levels of orbit. But because it's impossible for this electron to just cancel and be destroyed, it creates "forbbidden" orbits around the nucleus, where the wave will cancel. So if you filled an object full with all these electrons at one certain orbit (called the valence band) untill you couldn't fit any more in, what would happen if you run an electric current through it? the electrons passing through wouldn't get any resistance, since if they gave energy to the electron which take up the valence band they would fall into the forbidden zone. As i said this is very brief and there is more complexity to it then this, but basically the energy gap is this forbidden zone. I might point out too that if given enough energy, the electrons will "jump" from it's current level to the next "allowed" one without even beeing in between, this allowed one is called the conduction band. So this raises the question, how does something get from A to B without going in between?

Alot of modern technology like lasers, cameras, fluorescent light bulbs (forgive my spelling), solar cells, xerox machines and much more use this quantum effect to operate.

Anyway, hope you understood.

kashyap6552

well so many ans....bt still just check it out...it might gonna help u...http://en.wikipedia.org/wiki/Band_gap

saidvait

FEG is a rate of measure of the energy difference between valence band and conduction band ...in insulators like glass its of the order of 10 ev and in semiconductors its a bit low and it can be filled by supplying energy or increasing the temperature.....in conductors the valence band and conduction band overlap..thus favourin good conduction

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