An aluminium rod and a copper rod of equal length `1.0 m` and cross-sectional area. `1cm^(2)` are welded together as shown in figure. One end is kept at a temperature of `20^(@)C` and the other at `60^(@)C` Calculate the amount of heat taken out per second from the hot end. thermal conductivity of aluminium `=200Wm^(-1)C^(-1)` and of copper `=390Wm^(-1)C^(-1)` .

Answer

B, C

Explanation

As the aluminum rod and copper rod joined are in parallel
`Q/t=(Q/T)_(Al)+(Q/t)_(Cu)`
`implies(kA(theta_1-theta_2))/(l)`
`=(K_1 A(theta_1-theta_2))/(l)+(K_2 A(theta_1-theta_2))/(l)`
impliesK=K_1+K_2=(390+200)`
`=590`
`Q/t=(kA(theta_1-theta_2))/(l)` ltbrge(590xx1xx10^(-4)xx(60xx20)/1` ltbrge590xx1xx10^(-4)xx40`
`=59xx4xx10^(-2)=2.36watt.`