Three metal rods of same length and same cross - sectional area are connected in parallel. If their conductivities area 70, 110, 180 `Wm^(-1) K^(-1)` respectively, the effective conductivity (in `Wm^(-1) K^(-1))` of the combination is

Three metal rods of same length and same cross sectional area are connected in Parallel. If their conductivities are 70 Wm^(-1) K^(-1) , 110 Wm^(-1) K^(-1) and 180 wm^(-1) K^(-1) respectively then effective conductivity of the combination is

Two metal rods of same length and same cross sectional area are connected in Series. If their conductivities are 120 Wm^(-1)K^(-1) and 240 Wm^(-1)K^(-1) then effective conductivity of the combination is

The metal rods of same length and same area of cross-section are connected in series. If their condcutivites are 120 Wm^(-1) and 240 Wm^(-1) K^(-1) the effective conductivity of the combination is

Three metal rods of same lengths and same area of eross-section having conductivities 1,2,3 units are connected in series. Then theireffective conductivity will be

Two identical metal wires of thermal conductivities K_(1) and K_(2) respectively are connected in series. The effective thermal conductivity of the combination is :

Three metal rods of same lenghs and same area of cross sections having conductivities 1,2,3, units are connected in series Then their effective conductivity will be .

Three metal rods of same lengths and same area of cross-section having conductivities 1, 2, 3 units are connected in series. Then their their effective conductivity will be

Two rods of same length having conductivities 60 Wm'k, 40 Wm'K' and areas 0.2 m^(@), 0.3m^(2) are connected in Parallel to each other. The effective conductivity of the combination is