Physics Current Electricity MDCAT 2012
PMDC Verified Question 103 of 112
Which one of the following is I-V curve of a junction diode?

Current (I) Voltage (V) Vk ~0.7V
A
A straight vertical line
B
A straight horizontal line
C
A non-linear curve showing exponential rise in forward bias
D
None of these
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: A non-linear curve showing exponential rise in forward bias
Concept:

A p-n junction diode is a non-ohmic device. It does not obey Ohm's Law (where \( V \propto I \)).

Solution:

  • For a diode, current only begins to flow significantly after the forward voltage exceeds the depletion barrier (e.g., 0.7V for Silicon).


  • After this knee voltage, the current rises exponentially.


  • Therefore, the I-V graph is a non-linear curve, typically rising sharply in the first quadrant.


Why other options are incorrect:

  • Opt A & B: These represent zero resistance and infinite resistance respectively, which do not apply to a standard diode.


  • Straight line through origin: Would represent a perfectly ohmic resistor, not a diode.

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.

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.