Heat Conductivity

A brass disk has six metal spokes (each 15 cm long) radiating from it. A seventh spoke serves as the arm which fits in a clamp supporting the apparatus on a stand. Five of the these spokes are made of Brass, Copper, Iron, Nickel-Silver, and Silver, all having identical cross-sections. The sixth one is made of Iron, but with twice the diameter of the other spokes. Small wax balls are stuck to the end of each spoke and the brass disk is placed right over a Bunsen burner. Ideally, they should fall off in the following order: Copper (1.083), Brass (0.330), large Iron (0.167), small Iron (0.167), Nickel (0.135), and Nickel-Silver (0.105). The values in parenthesis are their respective thermal diffusivity in cm2/sec.

The net conductivity of the larger rod is twice that of the smaller rod: its cross-section is four times larger but it loses thermal energy twice as fast.