An electric wire 0.25 mm diameter e1 = 0.4
is placed within a tube of 2.5 mm diameter, = 0.6 having
negligible thickness. This tube is placed concentrically within a tube of 5 mm
diameter, = 0.7.
Annular spaces can be assumed to be evacuated completely. If the surface
temperature of the outer tube is maintained at 5C, what must be the
temperature of the wire so as to maintain the inner tube at 120C?
Heat lost by the wire to the inner tube =
Heat lost by the inner to the outer tube.
Substituting the given values, find T1.