A copper rod of length 75 cm and an iron rod of length 125cm are joined together end to end . Both are of circular cross section with diameter 2 cm . The free ends of the copper and iron are maintained at `100^@C` and`0^@C` respectively . The surface of the bars are insulated thermally . The temperature of the copper -iron junction is [Thermal conductivity of the copper is `386.4 W//m-K ` and that of iron is `48.46W//m-K`].

Options

A. `100^(@)C`
B. 0^(@)C`
C. 93^(@)C`
D. 50^(@)C`

Explanation

Let temperature of copper and iron juction is `theta`

`therefore "Temperature of juction"(theta)=(K_(1)l_(2)theta_(1)+K_(@)l_(1)theta_(2))/(K_(1)l_(2)+K_(2)l_(1))`
`=(386xx125xx100+48.46xx75xx0)/(386.4xx125+48.46xx75)`
`=(48,300xx100)/(48,300+36344.5)`
= `0.93xx100 = 93^(@)C`