Two identical square rods of metal are welded end to end as shown in figure (i), 20 calories of heat flows through it in 4 minutes. If the rods are welded as shown in figure (ii), the same amount of heat will flow through the rods in

Options

A. `1` minute
B. `2` minute
C. `4`minute
D. `16` minute

Answer

A

Explanation

Fig `A` : `20 = ((100 -0)/((L)/(kA) + (L)/(kA))) xx 4 …. (i)`
Fig `A` : `20 = Q = (100-theta) [(kA)/(L) + (kA)/(L)]t …..(ii)`
Equation (i) -:(ii) `1= (4//2)/(2//t) t = 1` min.