Formation of energy bands in solids, Electrical Engineering

Describe in brief the Formation of energy bands in solids and hence explain how it helps to classify the solid in to conductors and insulators.

Energy Bands in Solids

According to K conig-Penney model it has been observed that in solids energy bands exist instead of single energy levels. The formation lf energy bands in solids can also be visualized from the following experiment. In an isolated atom, the electrons are tightly bound and have discrete sharp energy levels. When the wave functions of electrons in different atoms overlap the energy levels corresponding to these wave functions split resulting two levels. The splitting depends on the extent of overlapping or the distance between the atoms. If more and mere atoms are brought closer, more and more closely spaced levels are formed. In a solid of N atoms each main energy level splits into a band of N closely spaced energy levels. The levels are so close that they form energy band. The energy separation E between successive levels in an allowed band is of the order of e V. The width of the energy band depends on the extent of overlapping of orbital. Hence the outer band is very wide. As we go to inner energy levels or orbits the width of the energy bands decreases. The energy bands are separated by gaps called forbidden energy gap. The splitting of energy levels and the energy bands at equilibrium interatomic distance are shown in the figure. The energy band containing valence electron is called valence band. The energy band above the valence band is called conduction band. The electrons forming the covalent bands between the atoms are supposed to be present in the covalent band. The excited electrons, which are removed from the atoms and move freely in the crystal, are called free electrons or conduction electrons. They are supposed to be present in the conduction band. The electrical properties of solids depend on the condition of valence band, conduction band and the forbidding energy gap in between them. The inner energy bands have no significance. 

 

Posted Date: 7/2/2012 9:56:06 PM | Location : United States







Related Discussions:- Formation of energy bands in solids, Assignment Help, Ask Question on Formation of energy bands in solids, Get Answer, Expert's Help, Formation of energy bands in solids Discussions

Write discussion on Formation of energy bands in solids
Your posts are moderated
Related Questions
What is Q-switching in laser ? Give its application. Discuss the elementary idea of mode locking. Generation of high power pulses There are three basic techniques to gene

The small electronics consultancy company that you work for has been commissioned to design a portable mixed signal heart rate monitor unit for the National Health Service. You hav

Q. Sketch the timing diagram for a 4-bit ripple counter which uses T flip-flops.

Q. A 230-V, single-phase, 60-Hz source supplies two loads in parallel. One draws 10 kVA at a lagging power factor of 0.80 and the other draws 6 kWat a lagging power factor of 0.90.

A three-phase, six-pole, wye-connected synchronous generator is rated at 550 V and has a synchronous reactance Xs = 2 . When the generator supplies 50 kVA at rated voltage and a p

Q. Explain working of Inverting Summing Amplifier? The circuit of Figure is extended by adding other input points, as shown in Figure. Because of the virtual ground at terminal

Astigmation control: In most modern oscilloscopes there is an additional focusing control marked Astigmation . This is used to correct an effect which exactly is analogous to

can I get matlab code for out of band radiation reduction ofdm system

Explain the chemical properties of insulating materials. Chemical properties - Chemical resistance: Presence of gases, acids, water, alkalies and salts influences different

Explain DAA instruction. DAA: The DAA instruction follows the instruction ADC or ADD to adjust the result in a BCD result. The DAA instruction performs only with the AL registe