Which expression gives the rate P at which thermal energy is conducted through a uniform rod of length L and cross-sectional area A with thermal conductivity k when its ends are maintained at temperatures T1 and T2 (T1>T2)?
a) P=L2kA(T1−T2)
b) P=LkA(T1−T2)
c) P=2LkA(T1−T2)
d) P=LkAln(T2T1)