Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 55 of 494
An isolated crystal of a \( \text{P-type} \) extrinsic semiconductor carries a net electrical charge of:
A
Strongly positive
B
Weakly positive
C
Weakly negative
D
Zero (neutral)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Zero (neutral)
Concept:

Doping a semiconductor crystal with neutral impurity atoms does not alter the overall electrical neutrality of the bulk crystal lattice.

Formula:

$$Q_{\text{net}} = 0$$

Solution:

  • A P-type semiconductor is created by adding neutral trivalent impurity atoms (e.g., Indium, Boron) to a neutral tetravalent crystal (Silicon).


  • Each created mobile hole is balanced by a stationary negatively charged acceptor ion fixed in the lattice, making the net macroscopic charge zero.


Why other options are incorrect:

  • Option A: Confuses majority positive charge carriers (holes) with the net charge of the entire material.


  • Option B: The presence of positive mobile holes is perfectly balanced by bound negative acceptor ions.


  • Option C: N-type semiconductors also remain electrically neutral; neither type carries net negative charge macroscopically.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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