190. The change in carrier concentration along the length of a semiconductor is called
A. Diffusion length
B. A concentration gradient
C. Recombination rate.
D. Mobility.

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191. When a freeelectron is recaputed by a hole and fills the hole, the process is called
A. Recombination
B. Diffusion
C. Thermal equilibrium
D. Lifetime.

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192. The movement of charges from an area of high carrier concentration to an area of lower carrier concentration is called
A. Gradient
B. Recombination
C. Diffusion
D. Lifetime.

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193. When the rate at which hole-electron pairs are thermally generated is equal to the rate at which holes and electrons recombine
A. there exists a gradient in the semiconductor.
B. there must be a diffusion of charges.
C. the semiconductor is in thermal equilibrium.
D. there must be more holes than free electrons.

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194. The rate at which diffusion occurs
A. depends on the gradient only
B. depends on the mobility only
C. depends on the gradient and the mobility
D. is always the same.

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195. The movement of carriers by p.n applied voltage is called
A. Drift current
B. Diffusion current
C. Mobility.
D. Concentration

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196. For extrinsic semiconductors at medum temperatures, the change in resistivity as temperature changes is primarily due to
A. change in carrier concentration.
B. change in the charge of each carrier.
C. change in the gradient
D. change in carrier mobilities.

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