Three identical conducting rods are connected as shown in figure. Given that `theta_a = 40^@C`, `theta_c = 30^@C` and `theta_d = 20^@C`. Choose the correct options.

Options

A. temperature of junction b is `15^@C`.
B. temperature of junction b is `30^@C`
C. heat will flow from c to b
D. heat will flow from b to d

Answer

B, D

Explanation

`H_1 = H_2 + H_3`
`:. (40-theta)/R = (theta -20)/R + (theta -30)/R`
where, R = thermal resistance of each rod
Solving this equation, we get
`theta = 30^@C`
Heat flows from higher temperature to lower temperature.