The container `A` is constantly maintained at `100^(@)C` and insulated container `B` in the contains ice at `0^(@)C` Different rods are used to connect them For a rod made of copper, it takes 30 mintes for the ice to melt and for a rod of steel of same cross-section taken in different experiment it takes 60 minutes for ice to melt. When these rods are simultaneously connected in parallel, the ice melts is
.

Options

A. 15 minutes
B. 20 minutes
C. 45 minutes
D. 90 minutes

Answer

B

Explanation

Q =it where I = heat flow rate `= (DeltaT)/(R ) = (100)/(R )`
`:.Q=((100)/(R_(1)))(30)rArrR_(1)=((100)/(Q))xx30`
Also `:.Q = ((100)/(R_(2)))xx30 rArrR_(2) = ((100)/(Q)) xx 60`
Now `Q=((1)/(R_(1))+(1)/(R_(2)))t_(reqd)`
`:. t_(reqd) = (Q)/(((Q)/(100))xx(1)/(30)((Q)/(100))xx(1)/(60))=20min` .