Thermodynamics Part 2

Two identical metal wires of thermal conductivities K1 and K2 respectively connected in series are represented as followsThe above figure can also be represented as
Therefore, the effective thermal conductivity of the combination will be given by
R‌eff ‌=‌

I

K1A

+‌

I

K2A

=‌

2l

KeqA

⇒‌‌‌

2

Keq

=‌

K1+K2

KlK2

⇒Keq=‌

2K1K2

K1+K2