The minority carrier life time and diffusion constant in a semiconducting materi

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Question
The minority carrier life time and diffusion constant in a semiconducting material are 100 ?s and 100 cm²/s respectively. The diffusion length of carriers is
Options
A. 0.1 cm
B. 0.01 cm
C. 0.0141 cm
D. 1 cm

Correct Answer

0.1 cm

Explanation

Diffusion length = sqrt(Carrier life time x Diffusion constant) = (100 x 10^-6 x 100)^0.5 = 0.1 cm.

Materials and Components problems

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1. The attraction between the nucleus and valence electron of copper atom is
Options
A. zero
B. weak
C. strong
D. either zero or strong

2. Assertion (A): In a perfect capacitor, the current density is given by ? ?₀E₀?^'_rcos(?t + 90�), where ?_r^' is real part of dielectric constant.
Reason (R): In a perfect capacitor, dielectric losses are zero.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

4. Assertion (A): Electronic and Ionic polarization in a polyatomic gas are independent of temperature.
Reason (R): The orientation polarization is independent of temperature.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

5. Assertion (A): From the slope of the line in Figure, we can find permanent dipole moment of the molecules.
Reason (R): Total polarization of a polyatomic gas is given by P = N(a_e + a_i + ?²_p / 3kT)E.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

6. If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature
Options
A. both will have equal value of resistivity
B. both will have equal negative resistivity
C. resistivity of germanium will be higher than that of silicon
D. resistivity of silicon will be higher than that of germanium

8. If a piece of wood is placed in a magnetic field
Options
A. the magnetic field will not be affected
B. the magnetic lines of force will bend towards the piece
C. the magnetic lines of force will bend away from the piece
D. the flux may increase or decrease

9. Assertion (A): For Diamond, ?_r = 1
Reason (R): Diamond is a diamagnetic material.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

10. In metals the valence electron wave functions are strongly perturbed by the presence of neighbouring atoms.
Options
A. True
B. False

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