Q. If resistance of the filament increases with temperature, what will be power dissipated in a $220\ V$- $100\ W$ lamp when connected to $110\ V$ power supply
A) $25\ W$
B) $< 25\ W$
C) $> 25\ W$
D) None of these
Explanation
(c) If resistance does not vary with temperature $P$ consumed
$= \left( \frac{V_{A}}{V_{R}} \right)^{2} \times P_{R} = \left( \frac{110}{220} \right)^{2} \times 100 = 25W$. But in second case resistance decreases so consumed power will be more than $25\ W$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.