Physics · 2020
JEE Main · 3 September 2020, Shift 1 · Q12
Model a torch battery of length l to be made up of a thin cylindrical bar of radius ' a ' and a concentric thin cylindrical shell of radius 'b'…
Model a torch battery of length $\displaystyle l$ to be made up of a thin cylindrical bar of radius ' a ' and a concentric thin cylindrical shell of radius 'b' filled in between with an electrolyte of resistivity $\displaystyle \rho$ (see figure). If the battery is connected to a resistance of value R, the maximum Joule heating in R will take place for :
Official answer
(2)
$\displaystyle \mathrm{R}=\frac{\rho}{2 \pi l} \ln \left(\frac{\mathrm{~b}}{\mathrm{a}}\right)$
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JEE Main 2020 Physics question, with the answer from NTA’s final answer key. Where our answers come from.