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 minutes. If the two coils, connected in parallel are used simultaneously.the same water will boil in time

Options

A. 9 min 20 sec
B. 5 min
C. 7 min 30 sec
D. 2 min 30 sec

Answer

A

Explanation

(a) In parallel `(1)R_(P) = (1)/(t_(1)) + (1)/(t_(2)) = t_(P) = (t_(1) t_(2))/(t_(1) + t_(2))`
`= (5 xx 10)/(5 + 10) = (50)/(15) = 3.33 m i n = 3 m i n 20 sec`