Previous IES Questions,Previous IES papers,IES questions on Electronics

PREVIOUS IES QUESTIONS(ECE)

1) A Hall effect tranducer can be used to measure…………..Displacement,Temperature and Magnetic Flux.

2) The ohm’s law for conduction in metals is……………….j=σE.

3) The unit of a thermalresistance of a semiconductor device is………… °C/Watt.

4) For n-type semiconductor with n=N_D and p=n_i²/N_D,the hole concentration will fall below the intrinsic value because some of the holes…………..recombine with the electrons.

5) As the fermi energy of silver is 8.8×10^{-19 joule,the velocity of the fastest electron in silver at 0°K (Given Rest mass of electron=9.1×10-31 Kg)} is …………1.39 ×106m/s.

6) n-type of silicon can be…………….. formed by adding impurities of phosphorous and also formed by adding impurity of arsenic.

7) An intrinsic semiconductor with energy gap of 1 eV has a carrier concentration N at temperature 200 KAnother intrinsic semiconductor has the same value of carrier concentration N at temperature 600K,What is the energy gap value for the second semiconductor …………….   (1/3) eV .

8)An intrinsic semiconductor isdoped lightly with p-type impurity.It is found that the conductivity actually decreases till a certain doping level is reached.Why does this occur?………..Because the mobility of both electrons and holes decreases.

9) The electron and hole concentrations n and p respectively obey the relation np=n_i^2 _where n_iis the intrinsic carrier density.This expression is valid for……….non-degenerate semiconductor under thermal equilibrium condition.

10) Why does mobility of electrons in a semiconductor decrease with increasing donor density?…….Doping increases the relaxation time of electrons.

11)An intrinsic semiconductor (intrinsic electron density=10¹⁶m^-3) is doped with donors to a level of 10²²m³

what is the hole density assuming all donors to be ionized? ………….10¹⁰m^-3.

12) Mobility is defined as ……………a diffusion velocity per unit field.

13) The mobility of electrons in a semiconductor is defined as the……..Drift velocity per unit electric field.

14) During an electron transition the energy gap in an indirect energy gap material like silicon…………

• the momentum of the electron changes,
• the potential energy of the electron changes,
• the kinetic energy of the electron changes.

15) For an n-type semiconductor…………….

• E_F lies below E_D at a room temperature(T).
• E_F lies above E_D as T—>0.
•  E_F= E_D   at some intermediate temperature. 


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