Physics Current Electricity MDCAT 2009
PMDC Verified Question 110 of 112
The deviation of I-V graph from the straight line is due to:
A
Decrease in temperature and decrease in resistance
B
Decrease in temperature and increase in resistance
C
Increase in temperature and increase in resistance
D
Increase in temperature and decrease in resistance
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Increase in temperature and increase in resistance
Concept:

Ohm's Law holds (a straight I-V line) only if physical conditions like temperature remain constant.

Solution:

  • As current increases, power dissipation \( (I^2R) \) increases, which raises the temperature of the conductor.


  • For metallic conductors, an increase in temperature causes an increase in resistance \( (\Delta R \propto \Delta T) \).


  • This increasing resistance causes the I-V curve to bend away from a straight line (the slope changes).


Why other options are incorrect:

  • Opt A & B: Heating (not cooling) occurs when current passes through a typical resistor.


  • Opt D: Resistance of metals increases, not decreases, with an increase in temperature.

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