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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 1
11.
At very high temperatures the extrinsic semi conductors become intrinsic because
drive in diffusion of dopants and carriers
band to band transition dominants over impurity ionization
impurity ionization dominants over band to band transition
band to band transition is balanced by impurity ionization
Answer: Option
Explanation:

Covalent bonds are broken.

12.
When a voltage is applied to a semiconductor crystal then the free electrons will flow.
towards positive terminal
towards negative terminal
either towards positive terminal or negative terminal
towards positive terminal for 1 μs and towards negative terminal for next 1 μs
Answer: Option
Explanation:

Since electrons are negatively charged they will flow towards positive terminal.

13.
Ferrite have
low copper loss
low eddy current loss
low resistivity
higher specific gravity compared to iron
Answer: Option
Explanation:

Ferrite is a low density material of composition with Fe2O3 x O, where x is a bivalent metal, such as Cobart, Ni, Mn. These magnetic materials having very low loss of current and used in high frequency circuit.

14.
In a p type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be
0.5 eV above valence band
0.28 eV above valence band
0.1 eV above valence band
below the valence band
Answer: Option
Explanation:

Addition of acceptor atom brings Fermi level closer to valence band.

15.
In an n-p-n transistor, the majority carriers in the base are
electrons
holes
both holes and electrons
either holes or electrons
Answer: Option
Explanation:

Emitter is n type and emits electrons which diffuse through the base.

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