The length of germanium rod is 0 . 925   cm and its area of cross section is 1   mm 2 . If for…

The length of germanium rod is 0.925 cm and its area of cross section is 1 mm2. If for germaniun ni= 2.5×1019 m-3,μh=0.19 m2/v-s,μe=0.39 m2/v-s, then the resistance of the rod is
  1. 2.5 kΩ
  2. 4.0 kΩ
  3. 5.0 kΩ
  4. 10.0 kΩ

Solution

Conductivity, σ=neμ

⇒σ=neμe+μh

⇒σ=2.5×1019×1.6×10-19×0.19+0.39

⇒σ=40.58=2.32

Resistivity, ρ=1σ=12.32=0.431 Ω

Resistance, R=ρLA=0.431×9.25×10-310-6

R=4 kΩ

Asked in: AP EAMCET 2021 (19 Aug Shift 2)

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