# Diffusion MCQ’s

This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Diffusion”.

1. 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
a) 100 A/cm2
b) 108 A/cm2
c) 0.01A/cm2
d) None

2. Which is the correct formula for the Jp?
a) Jp=qDdp/dx
b) Jp=pDdn/dx
c) Jp=-qDdp/dx
d) None

3. What is the SI unit of electron diffusion constant?
a) cm2/s
b) m2/s
c) m/s
d) none

4. What is the direction of the electron diffusion current density relative to the electron flux?
a) Same direction
b) Opposite to each other
c) Perpendicular to each other
d) At 270 degrees to each other

5. Which of the following parameter describes the best movement of the electrons inside a semiconductor?
b) Diffusion
c) Mobility

6. What does dn/dx represent?
d) None

7. In diffusion, the particles flow from a region of _______ to region of ___________
a) High, low
b) Low , high
c) High , medium
d) Low, medium

8. Which of the following term isn’t a part of the total current density in a semiconductor?
a) Temperature
b) µ
c) e
d) E

9. Calculate the diffusion constant for the holes when the mobility of the holes is 400cm2/V-s and temperature is 300K?
a) 1.035m m2/s
b) 0.035m m2/s
c) 1.5m m2/s
d) 1.9m m2/s

10. Calculate the diffusion constant for the electrons when the mobility of the electrons is 325cm2/V-s and temperature is 300K?
a) 0.85 m2/s
b) 0.084 m2/s
c) 0.58 m2/s
d) 0.95 m2/s