Figure shows an aluminium rod joined to a copper rod. Each of the rods has a length of 20cm and area of ccross section `0.20cm^(2)` . The junction is maintained at a constant temperature `40^(@)C` and the two ends are maintained at 80^(@)C` . Calculate the amount of heat taken out from the cold junction in one minute after the steady state is reached. The conductivities are `K_(Al)=200Wm^(-1)`^(@)C^(-1)` . and `K_(Cu)=400Wm^(-1)`^(@)C^(-1)` .

Answer

A, D

Explanation

`K_(Al)=200W//m^(@)C,`
`K_(U)=400W//m^(@)C,`
`A=0.2 cm^(2)=2xx10^(-5)m^(2)`
`l=20cm=2xx10^(-1)m`
Heat drawn per sec.
`Q_(Al)+Q_(Cu)=(K_(Al)xxAxx(80-40))/l`
+(K_(Cu)xxAxx(80-40))/l` ltbrge(2xx10^(-5)xx40)/(2xx10^(-1))[200+400]`
`=2.4 J.`
Heat drown per minute =2.4xx60=144J.`