just some true and false questions. 11. with an electric field in the x-directio
ID: 2266338 • Letter: J
Question
just some true and false questions.
11. with an electric field in the x-direction and a magnetic field in the z -direction, zero magnetoresistance means that j_y is zero for every charge carrier.
12. even if the relaxation time were not a function of energy, and if the material had spherical equal-energy surfaces, a non-zero magnetoresistance effect would be expeted if both electrons and holes were contributing to the conductivity.
13. the Hall mobility is given by the product of the conductivity and the Hall coefficient only for one-carrier conductivity.
14. The Hall mobility for and intrinsic semiconductor is identically zero.
15. When both electrons and holes contribute to the conductivity, the Hall coefficient is zero when n*mu_n=p*mu_p
16. electrons and holes are deflected in opposite directions by a magnetic field, when electrons or holes are flowing in response to an applied electric field.
17. for a fixed voltage, magnetic field and sample geometry, the measured Hall voltage is directly proportional to the Hall mobility.
18. To maintain constant cyclotron resonance frequency, larger effective masses require larger magnetic fields.
19. if over any temperature range the electrical conductivity is observed to decrease with increasing temperature, this means that the material is either a metal or a degenerate semiconductor.
20. if a plot of the logarithm of the conductivity vs 1/T gives a straight line in an n-type semiconductor, the slop of the line will be -E_d/(2k), where E_d is the donor ionization energy.
Explanation / Answer
11. False
12. False
13.True
14. True
15. True
16.False
17. True
18. True
19.True
20. True.
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