Two identical conducting rods are first connected independently to two vessels, one containing water at 100oC and the other containing ice at 0oC. In the second case, the rods are joined end to end and connected to the same vessels. Let q1 and q2g/s be the rate of melting of ice in two cases, respectively. The ratio of q1/q2 is

Initially the rods are placed in vessels as shown below.Qt=θ1−θ2R⇒Qt1=mLt=q1L=(100−0)R2  …..(i)Finally when rods are joined end to end as shown,⇒Qt2=mLt=q2L=(100−0)2R  ……..(ii)From equations (i) and (ii), q1q2=41IN series combination thermal resistance is four times to that in parallel combination of identical conducting rods .so in parallel combination heat flow is 4 times and hence rate of melting of ice will be 4 times to that in parallel combination.