question_answer

A rod AB is 1 m long. The temperature of its one end A is maintained at \[100{}^\circ C\] and other end B at WC. the temperature at a distance of 60 cm from point B is

A)  \[64{}^\circ C\]             

B)  \[36{}^\circ C\]

C)  \[46{}^\circ C\]            

D)  \[72{}^\circ C\]

Correct Answer: A

Solution :

 Let the temperature at distance 60 cm from point B is \[\theta \] where K = coefficient of thermal conductivity A = area of rod \[\frac{KA(100-\theta )}{40}=\frac{KA(\theta -10)}{60}\] Or \[\frac{100-\theta }{2}=\frac{\theta -10}{3}\] or        \[300-3\theta =26-20\] or             \[5\theta =320\] or              \[\theta =64{}^\circ C\]