393. A dielectric material in an electric field gets polarized. If the polarization is non-uniform, then there would be accumulation of
A. bound charge only on the surface
B. bound charge only within the material
C. bound charge within the material as well as on the surface
D. free charge on the surface of the dielectric

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394. An infinitely long dielectric cylinder of relative permitivity, E r is placed in air in a uniform electric field of magnitude E directed perpendicular to its axis. The stress withing the cylinder is
A.E1 + Er
B.1 + 2E
C. 2 + er
D. 2er

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395.  Consider the following statements in respect of energy bonds in a solid :1. Energy bands at high energy have more width than those bands at low energy.2. Low energy bands cprrespond to valence electrons3. There are always son* energy bands that are not filled. Which of these statements is/are correct?
A. 1, 2 and 3
B. 1 and 2
C. only 2
D. 1 and 3

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396.  When the wave vector of an electron in a metal is equal to half the reciprocal vecor values, the electron wave is
A. a travelling wave
B. a standing wave
C. an exponentially decaying wave
D. an exponentially rising wave

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397.  When a piece of metal has a temperature gradient between its two ends, an e.m.f. is observed to exist between those ends. This is known as
A. Peltier effect
B. Seebeck effect
C. Thomson effect
D. Hall effect

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398.  Two semiconductor materials A and B have carrier concentration values nA = 1 X 102Im-s and n = 4 X 1021M-3. Hall coefficients of the materials, RA and RB are in the ratio
A. 1 :2
B. 2 : 1
C. 1 :4
D. 4 : 1

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399.  Consider the following materials :1. Pure silicon 2. Aluminium 3. Doped silicon 4. Mica. The correct sequence in the order of their increasing electrical resistivity is
A. 1-2-3-4
B. 2-3-4-1
C. 2-3-1-4
D. 1-3-4-2

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