An electric kettle has two heating coils. When one coil is used, water in the kettle boils in $5$ minutes, while when second coil is used, same water boils in $10\,\min$. If the two coils, connected in parallel are used simultaneously, the same water will boil in time
Medium
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(a) In parallel $\frac{1}{{{t_p}}} = \frac{1}{{{t_1}}} + \frac{1}{{{t_2}}}$$ \Rightarrow $ ${t_p} = \frac{{{t_1}{t_2}}}{{{t_1} + {t_2}}}$
$ = \frac{{5 \times 10}}{{5 + 10}} = \frac{{50}}{{15}} = 3.33\,\min $$ = 3\,\min.\,20\,sec$
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