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Year 1997 : Paper 1

1. If the energy gap of semiconductor is 1.1 eV, then it would be -
a. Opaque to the visible light
b. Transparent to the visible light
c. Transparent to the ultraviolet radiation
d. Opaque to the infrared radiation

2. The skin depth of copper is found to be 66 um at 1 MHz at a certain temperature. At the same temperature and at 2 MHz, the skin depth would be approximately -
a. 47 μm
b. 33 μm
c. 92 μm
d. 122 μm

3. With increasing temperature, the electrical conductivity would
a. Increase in metals as well as in intrinsic semiconductors
b. Increase in metals but decrease in intrinsic semiconductors
c. Decrease in metals but increase in intrinsic semiconductors
d. Decrease in metals as well as in intrinsic semiconductors

4. Which one of the following statements is correct?
a. All electrostrictive materials are piezoelectric, and all piezoelectric materials are electrostrictive
b. Piezoelectric materials are a subset of electrostrictive materials
c. Electrostrictive materials are a subset of piezoelectric materials
d. Piezoelectricity and electrostriction are two totally independent properties of materials

5. Ferrites have
a. Low copper loss
b. Low eddy current loss
c. Low resistively
d. Higher specific gravity compared to iron

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