I. 8(a) What are alloys and how are they produced industrially? (b) Explain why alloys are usually used in preference over the pure metals. (c) Give the composition and uses of the following: (a ( (i) bronze (ii) brass (iii) duralumin (iv) type metal (v) soft solder. (d) Which of the following metals belong(s) to the first transition series? Chromium, lead, iron, magnesium, aluminium, manganese.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.