The end of two rods of different materials with their thermal conductivities, area of cross-section and lengths all in the ratio 1:2 are maintained at the same temperature difference. If the rate of flow of heat in the first rod is `4 cal//s`. Then, in the second rod rate of heat flow in `cal//s ` will be

Options

A. 1
B. 2
C. 8
D. 16

Answer

A

Explanation

`because (dQ)/(dt) = (K(pir^(2))Delta theta)/ l`
`implies` `((dQ)/(dt))_(2)/ ((dQ)/(dt))_(1) = (K_(2)xxr_(2)^(2) xx l_(1))/ (K_(1) xx r_(1)^(2) xx l_(2))= 1/2 xx 1/4 xx 2/1 `
`implies` `((dQ)/(dt))_(2) = ((dQ)/(dt))_(1)/4 = 4/4 = 1`