# Two rods of same length

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Two rods of same length  and materials transfer  a given amount  of heat in 12sec . When they are jointed end to end,  but when they are jointed  lengthwise they will transfer  same heat in same condition  willbe

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As per the question, if two rods are attached end to end to each other then it takes 12 sec. Now when they are attached parallel then its length halves and area will be doubled.

Heat flow is given as:

Q = KAΔT/L
so, T ∝ L/A
T' ∝ (L/2)/(2A)
T' ∝ (L/4A)
T' /T = (L/4A)/(L/A) = 4

T' = 1/4T = 1/4 X 12 = 3 sec

commented by (1.9k points)
But in this question,  12 sec is the time taken when connected  end to end means series  and we have to find when they are connected  length  wise  means parallel.    I am  still not able to understand  the question .  Can u clear my misunderstanding??
commented by (7k points)
Hey, I didn't notice that because its usual. If I consider your thought than the answer will be 3 secs as area doubles and length halves.
commented by (1.9k points)
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Ok .....
commented by (7k points)
+1
Is it clear how length halved now with the image.