given: \(i=50 \mathrm{~A}, \mathrm{R}=10 \Omega\),
\(\mathrm{t}=4.0 \mathrm{mins}=4 \times 60 \mathrm{~s}\)
\(M_w=500 \mathrm{~g}=0.5 \mathrm{~kg}\)
required \(\Delta \theta=\) ?ssuming no heat loss, then heat generated by \(\operatorname{cost}=\) heat absorbed by water
\begin{array}{l}
\Rightarrow l^2 \mathrm{Rt}=m c \Delta \theta \\
\Delta \theta=\frac{l^2 \mathrm{Rt}}{\mathrm{mc}}
\end{array}