p-n Junction & Biasing Challenge
25 NEET-standard questions on how a p-n junction forms (diffusion, drift, depletion region, barrier potential), the diode symbol, and forward and reverse bias. Answer each one. If you get it wrong, Vidya Ma’am explains it with an animated movie you can control, a slider to play with, and a step-by-step solution. Then try again.
NCERT Physics XII Part II · Ch. 14 · pp. 333–335Keys: A–D or 1–4 to answer
🧠 Formula memory tricks (open before you start)
FormationDiffusion (many to few) builds fixed ions; the ions’ field drives drift the other way.Equilibrium: diffusion = drift, net current 0
Depletion regionImmobile + ions on n-side, immobile − ions on p-side. Thickness ≈ 0.1 µm.Field points n → p
Barrier potentialn-side is positive. NCERT gives no V₀ number here; typical Si value about 0.7 V (threshold ~0.7 V Si, ~0.2 V Ge, p.337).
Forward biasp to +. Barrier V₀ − V, layer narrows, current in mA.Minority carrier injection
Reverse biasn to +. Barrier V₀ + V, layer widens, current only a few µA.Almost independent of V
Diode symbolThe arrow points p → n: conventional forward current.
right first tryfixed after explanationstill to fix
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