I recently came across the formula $Q=kA(T_2-T_1 )t/l$. I have a question regarding the interpretation of the formula.

1.)Does Q refer to the amount of heat that flows through a cross sectional area A, of a conductor in the steady state, having length $l$, having temperatures of $T_2$ and $T_1$ at its ends, in a time interval of $t$?

2.)Thus, if I have a conductor having non-uniform cross sectional area, and I want to find out the amount of heat that flows through a particular cross sectional area $A_1$, will I be able to use the formula? $Q=kA_1(T_2-T_1)t/l$.

3.)I am basically asking whether A refers to the cross sectional area of a uniform conductor or any particular cross sectional area of a non-uniform conductor.

I am in class 11, so please avoid any complicated answers. Thanks in advance!! Please answer each part of the question individually


1 Answer 1


The formula you stated is only valid when the system is in steady state and the conductor has uniform cross-sectional area. If the area changes, then you will have to use integration to calculate $k$ for the whole body.


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