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# Test: Diffusion

## 10 Questions MCQ Test Electronic Devices | Test: Diffusion

Description
This mock test of Test: Diffusion for Electrical Engineering (EE) helps you for every Electrical Engineering (EE) entrance exam. This contains 10 Multiple Choice Questions for Electrical Engineering (EE) Test: Diffusion (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Diffusion quiz give you a good mix of easy questions and tough questions. Electrical Engineering (EE) students definitely take this Test: Diffusion exercise for a better result in the exam. You can find other Test: Diffusion extra questions, long questions & short questions for Electrical Engineering (EE) on EduRev as well by searching above.
QUESTION: 1

### What is the SI unit of electron diffusion constant?

Solution:

J=eDdn/dx
So D=q*m/ (q*s*(1/m))
=m2/s.

QUESTION: 2

### Calculate the diffusion current density when the concentration of electron varies from the 1*1018 to 7*1017 cm-3 over a distance of 0.10 cm.D=225cm2/s

Solution:

J=eDdn/dx
J=1.6*10-19*225*(1018-(7*1017))/0.1
=108A/cm2.

QUESTION: 3

### Which is the correct formula for the Jp?

Solution:

Jp is negative for the p type of semiconductors.

QUESTION: 4

What is the direction of the electron diffusion current density relative to the electron flux?

Solution:

From the graph between electron concentration and the distance, we can see that the direction of the electron diffusion current density is opposite to the electron flux.

QUESTION: 5

In diffusion, the particles flow from a region of _______ to region of ___________

Solution:

Diffusion is the process of flow of particles form the region of the high concentration to a region of low concentration.

QUESTION: 6

Which of the following parameter describes the best movement of the electrons inside a semiconductor?

Solution:

Mobility is defined as the movement of the electrons inside a semiconductor. On the other hand, velocity gradient is the ratio of velocity to distance.

QUESTION: 7

Which of the following term isn’t a part of the total current density in a semiconductor?

Solution:

J=enµE+epµE+eDdn/dx-eDdp/dx
So, temperature isn’t a part of the equation.

QUESTION: 8

What does dn/dx represent?

Solution:
QUESTION: 9

Calculate the diffusion constant for the holes when the mobility of the holes is 400cm2/V-s and temperature is 300K?

Solution:

: Dp=VT*μn
= (1.38*10-23*300*400*10-2)/ (1.6*10-19)
= 1.035m m2/s.

QUESTION: 10

Calculate the diffusion constant for the electrons when the mobility of the electrons is 325cm2/V-s and temperature is 300K?

Solution:

Dn=VT*μn
= (1.38*10-23*300*325*10-2)/ (1.6*10-19)
= 0.084 m2/s.