A3-mm-diameter electrical wire is insulated by a 2-mm-thick rubberized sheath (k = 0.13 w/m·k), and the wire/sheath interface is characterized by a thermal contact resistance of r, e=3x1 convection heat transfer coefficient at the outer surface of the sheath is 15 w/m2 . k, and the temperature of the ambient air is 20°c. if the temperature of the insula- 0-4m2. k/w. the tion may not exceed 50'c, what is the maxtimun allow- able electrical power that may be dissipated per unit length of the conductor? what is the critical radius of the insulation?