Two rods of same length and transfer a given amount of heat 12 second, when they are joined as shown in figure (i). But when they are joined as shwon in figure (ii), then they will transfer same heat in same conditions in

Options

A. 24 s
B. 3 s
C. 1.5 s
D. 48 s

Answer

D

Explanation

Let the heat transfered be Q.
when rods are joined end to end. Heat transfered by each rod
`Q = (K(2A)Deltatheta)/l xx 12` .....(i)
when rods are joined lengthwise,
`Q = (KADeltatheta)/(2l) t` .......(ii)
As the same amount of heat is transfered
`therefore` From Eqs. (i) and (ii) , we get t = 48 s