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Water boils in an electric kettle in 10 ...

Water boils in an electric kettle in 10 minutes after being switched on .How will you modify the heating coil to boil water is 5 minutes using the same source of power ?

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For the source of power of the same emf , V= constant . As equal amount of heat is produced in the two cases , we have
`(V^(2)t_(1))/(R_(1))=(V^(2)t_(2))/(R_(2)) , "because heat produced "oo(V^(2)t_(1))/(R).`
`thereforeR_(2)=R_(1)(t_(2))/t_(1)=R_(1)xx(5"min")/(10"min")=(1)/(2)R_(1)`
This means that a heating coil with half the resistance compared to the initial one , is to be used .
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