Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power If the length of filament of a heater is reduced by 10%, the power of the heater will increase by about 9% increase by about 11% increase by about 19% increase by about 10% Reveal answer Fill a bubble to check yourself D Correct answer Explanation $P=\dfrac { { V }^{ 2 } }{ R } \ R=\dfrac { \rho l }{ A } \ \therefore P=\dfrac { { V }^{ 2 }A }{ \rho l } $$ \therefore P\alpha \dfrac { 1 }{ l } \quad $ [Keep in $\dfrac{v^2A}{\rho }$ constant]$\therefore$ with reduction of $l$ by $10\%$ power will increase by $10\%$.