An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m2). The critical thickness of insulation will be
A. 25 mm
B. 40 mm
C. 160 mm
D. 800 mm
Answer: Option A
Solution (By Examveda Team)
Critical radius of insulation for cylinder = k/h.K = thermal conductivity of cylinder
$$\frac{{0.15}}{6} = 0.025\,{\text{m}} = 25\,{\text{mm}}{\text{.}}$$
This Question Belongs to Mechanical Engineering >> Heat And Mass Transfer
Critical thickness for cylindrical conductor = k/h = 0.15/6 = .025m = 25mm.