Question

Two identical plates of different metals are joined to form a single plate whose thickness is double the thickness of each plate. If the coefficients of conductivity of each plate are 2 and 3 respectively, then the conductivity of the composite plate will be

• A. 5
• B. 2.4
• C. 1.5
• D. 1.2

Answer 1

The correct option is D 1.2

Two identical plates of different metals. Coefficient of conductivity of each plate $=2$ and $3$.

${\sigma }_1=2$

${\sigma }_2=3$

thickness is double the thickness of each plates.

$\frac{2\times 3}{2+3}=\frac{6}{5}=1.2$