Question

1) You notice that the ceramic coffee mugs in the office get too hot to hold about 15 seconds after pouring in the hot coffee. The wall thickness of the cup is 2.5mm. (a) What, approximately, is the thermal diffusivity of the ceramic of the mug? (b) Given that the volume specific heat of solids, pCp, is more or less constant at 2* 106J/m3 K, what approximately is the thermal conductivity of the cup material? (c) If the cup were made of a metal with a thermal diffusivity of 8 * 10-5m2/s, how long could you hold it?

Answer 1

Qus'e Giveni t=158 ; x=2.5 mm= 2.5x10²m solen? a) Thermal diffusivity of the Ceramica ["Taking it as onder of a 2x X/~kt an x4 x² 4 t 4 an (2.5x103)2 4X 15 x~ 1.04 16410 -7 ma19 (en) co f(p = 2x105 5/m²K Thermal Conductivity; - (K) x = K Cla Sce K= 8ea k = 2x100 x 1.04 16 x 16 K=0.2083 W/mk (c) of x=8x10 3 m/ 2xx x2 t~ 4. (2.5x103) 2 t IR? 0.019538 4 X -$ + = 0.019538