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

`(dQ//dt)_(1) = (dQ//dt)_(2) + (dQ//dt)_(3)`
`KQ (T-0)//1 = KA (90-T)//l + KA (90-T)//l, T = 60^(@)C`