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A potential barrier of 0.2 V exists across a p-n junction. If the depletion region is 5.0×10⁻⁷ m wide, the intensity of the electric field in this region is ________ V m⁻¹.

Asked in GSEB Board July 2018 · Depletion region and barrier potential

• (1) 1×10⁵
• (2) 4×10⁵
• (3) 1×10⁶
• (4) 2×10⁵

Step-by-step solution

Why the other options are wrong

• (1) No single slip produces 1×10⁵; it is four times too small. Sanity check: (0.2)/(5.0×10⁻⁷) has mantissa 0.2/5.0 = 0.04 and so comes to 4×10⁵.
• (3) 1×10⁶ is the answer to the commoner version of this question, the one with a 0.50 V barrier: 0.50/(5.0×10⁻⁷) = 1×10⁶. Here the barrier is 0.2 V.
• (4) 2×10⁵ comes from rounding the width to 10⁻⁶ m and keeping the 2 of 0.2: 0.2/10⁻⁶ = 2×10⁵. The width is 5.0×10⁻⁷ m, which is half of that.

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