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A current i passes through a wire of length $l$, radius of cross-section $r$ and resistivity $\rho$. The rate of heat generation is
  • A$\frac{{{i^2}l\rho }}{{\pi {r^2}}}$
  • B${i^2}{\left( {\frac{{l\rho }}{{\pi {r^2}}}} \right)^2}$
  • C${i^2}l\,\rho \,/\,r$
  • D$i\,l\,\rho \,/\,r$
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