Physics - Current Electricity Question with Solution | TestHub

Heat taken by water when its temperature changes from $20^{\circ }\mathrm{C}$ to $100^{\circ }\mathrm{C}$. $$\begin{array}{rl}{H}_1& =mc\left({\theta }_2-{\theta }_1\right)=1000\times 1\times (100-20)\mathrm{cal}\\ & =1000\times 80\times 4.2\mathrm{J}\end{array}$$ Heat produced in time $t$ due to current in resistor $H_2=Vit=220\times 4\times t\mathrm{J}$ According to question, $$\begin{array}{l}220\times 4\times t=1000\times 80\times 4.2\\ \Rightarrow t=\frac{1000\times 80\times 4.2}{220\times 4}=381.8\mathrm{s}=6.3\min \end{array}$$