1.

Which of the following circular rods, (given radius r and length l) each made of the same material and whose ends are maintained at the same temperature diff. will conduct most heat ?

Answer»

`R=2r_(0),L=2l_(0)`
`r=r_(0),l=2l_(0)`
`r=2r_(0),l=l_(0)`
`r=r_(0),l=l_(0)`.

SOLUTION :`(c ):(dQ)/(dt)=KA(dT)/(DX)`
Since `A=pir^(2)` and `dx=l`
`:.(dQ)/(dt)prop(r^(2))/(l)`
Now `(r^(2))/(l)` will be maximum
when `r=2r_(0)` and `l=l_(0)`
Coorect choice is (c ).


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