Three rods made of the same material and having the same cross-section have been joined as shown in the figure. Each rod is of the same length. The left and right ends are kept at `0^@C` and `90^@C`, respectively. The temperature of junction of the three rods will be
(a) `45^@C` (b) `60^@C`
(c) `30^@C` (d) ` 20^@C`.

Options

A. `45^(@)C`
B. `60^(@)C`
C. `30^(@)C`
D. `20^(@)C`

Answer

B

Explanation

`(kA(90-T))/(l) + (kA(90-T))/(l) = (kA(T-0))/(l)`
`implies 90-T + 90 - T = T`
`implies 3T = 180 implies T= 60^(@)C`