Question

Six identical conducting rods are joined as shown in figure. Points A and D are maintained at temperatures 200ºC and 20ºC respectively. Then temperature of junction B will be - A) 120ºC (B) 100ºC (C) 140ºC (D) 80ºC ​

Answer 1

answer : option (C) 140°

explanation : Let R is thermal resistance of each rod.

first of all, find equivalent thermal resistance between B and C.

[ using electrical concepts to find equivalent thermal resistance cause both concepts are similar.]

so, Req = R

now, thermal resistance between A and B = R

thermal resistance of B and D = R + R = 2R

now heat flows through A and B = heat flows through B and D

so, change in temperature between A and B/thermal resistance between A and B = change in temperature between B and D/thermal resistance between B and D

or, (200 - T)/R = (T - 20)/2R

or, 2(200 - T) = T - 20

or, 400 - 2T = T - 20

or, 3T = 420

or, T = 140

hence, temperature of junction B will be 140°C

option (C) is correct choice .

Answer 2

Explanation:

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