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The coefficient of the thermal conductiv...

The coefficient of the thermal conductivity of copper is 9 times that of steel . In the composite sylindrical bar shown in the figure , what will be the temperature at the junction of copper and steel ?

A

`75^(@)`

B

`33^(@)`

C

`65^(@)`

D

`25^(@)`

Text Solution

Verified by Experts

The correct Answer is:
A
Let T be the temp. of junction.
`:.` In equilibrium `Q_(1)=Q_(2)`.
`:.(k_(1)A(100-T)t)/(18)=(k_(2)A(T-0)t)/(6)`
`rArr(9k_(2)(100-T))/(18)(k_(2)T)/(6)rArrT=75^(@)C`
Correct choice is (a).
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