A copper rod of 88 cm and an aluminium rod of unknown length have their increase in length independent of increase in tmperature. The length of aluminium rod is : ($$\alpha $$_Cu = 1.7 × 10^–5 K^–1 and $$\alpha $$_Al = 2.2 × 10^–5 K^–1)

When a block of mass M is suspended by a long wire of length L, the length of the wire becomes (L + $$l$$). The elastic potential energy stored in the extended wire is :

A small hole of area of cross-section 2 mm² present near the bottom of a fully filled open tank of height 2 m. Taking g = 10 m/s², the rate of flow of water through the open hole would be nearly :

The unit of thermal conductivity is :