The macroscopic magnetic properties of a substance are a consequence of magnetic moments associated with individual electrons. The electrons in an atom revolved around the nucleus in different orbits. Each electron in an atom has magnetic moments that originate from the following sources. The orbital magnetic moment of electrons (the motion of electrons in the
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Definition : When conductor (metal or semiconductor) carrying a current is placed in a transverse magnetic field, an electric field is produced inside the conductor in a direction normal to both the current and the magnetic field. This phenomenon is known as “Hall effect” and the generated voltage is called “Hall voltage”. This effect is
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S.NO Intrinsic semiconductors Extrinsic semiconductors 1. Semiconductor in a pure form is called intrinsic semiconductor. Semiconductor which are doped with impurity is called extrinsic semiconductor. 2. Here the charge carriers are produced only due to thermal agitation Here the charge carriers are produced due to impurities and may also be produced due to thermal agitation.
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The variation of carrier concentration with temperature for a n-type semi conductor is shown in Fig. At 0K both the conduction band and valence band are free from any charge carriers and hence conductivity is zero. Now, when the temperature is slowly increased, the donor atoms get ionized and hence, the electron concentration in conduction band increased.
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S.No. n-type semiconductor p-type semiconductor 1. N-type semiconductor is obtained by doping an intrinsic semiconductor with pentavalent impurity. P-type semiconductor is obtained by doing an intrinsic semiconductor with a trivalent impurity. 2. Here electrons are majority carriers and holes are minority carriers. Here holes are majority carriers and electrons are minority carriers. 3. It has
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A semiconductor to which a suitable impurity in a controlled rate is added to increase its conductivity is called an extrinsic semiconductor. Based on the type of impurity added they are classified into two types. They are, n-type semiconductor p-type semiconductor N-type semiconductors Definition: When a small amount of pentavalent impurity or element with five
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Based on the composition of elements they are classified into two types. They are S.No. Elemental semiconductors Compound semiconductors 1. These are made from single element These are made from compound (mixed elements) 2. These are made from IV group elements of periodic table These are made from III and V [or] II and VI
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Classical free electron theory could not explain many physical properties. This drawbacks of classical theory can be rectified using quantum theory. The failures of classical theories were removed by Sommerfield in 1928. He developed a new theory applying quantum mechanical concepts and Fermi-Dirac statistics to the free electrons in the metal. This theory is called
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The classical free electron theory has been successfully applied to explain the various properties of metal. It is used to verify Ohm’s law It is used to derive Wiedemann-Franz law. It explains the electrical and thermal conductivities of metals. It explains optical properties of metals. It correctly predicts different resistivities of various metals. Limitations of
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The electrical conductivity is defined as the rate of electric charges flows across a unit area in a unit time per in a conductor per unit potential gradient (or) electric field. It is denoted by σ. [latex] \begin{aligned} \sigma & =\frac{\mathrm{Q}}{\mathrm{AtE}} \quad\left(\text { Since } \mathrm{J}=\frac{\mathrm{I}}{\mathrm{A}}: \mathrm{I}=\frac{\mathrm{Q}}{\mathrm{t}}: \mathrm{J}=\frac{\mathrm{Q}}{\mathrm{At}}\right) \\ \sigma & =\frac{\mathrm{J}}{\mathrm{E}} \mathrm{ohm}^{-1} \mathrm{~m}^{-1} \end{aligned}
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