JEE Main 2015 Physics question

Not in JEE Advanced syllabus

In an unbiased p - n junction electrons diffuse from n-region to p-region because:

(1)electrons travel across the junction due to potential difference
(2)only electrons move from n to p region and not the vice - versa
(3)electron concentration in n - region is more as compared to that in p - regionCorrect
(4)holes in p - region attract them

Answer: (3)

Solution

Diffusion is driven purely by a concentration gradient, not by any field or attraction. In an unbiased junction the n-side is rich in free electrons and the p-side is poor in them, so electrons diffuse from n to p, and symmetrically holes diffuse from p to n — option (3). Option (1) is wrong

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Question ID VK-115252