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##### (Solution) - An electronic device such as a power transistor mounted on a

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An electronic device, such as a power transistor mounted on a finned heat sink, can be modeled as a spatially isothermal object with internal heat generation and an external convection resistance.

(a) Consider such a system of mass M, specific heat c, and surface area AS' which is initially in equilibrium with the environment at T?. Suddenly, the electronic device is energized such that a constant heat generation Eg (W) occurs. Show that the temperature response of the device is where

0 == T ? T(?) and T(?) is the steady-state temperature corresponding to t ? ?; ?i = Ti - T (?); Tj = initial temperature of device; R = thermal resistance I/hAs; and C = thermal capacitance Mc.

(b) An electronic device, which generates 60 W of heat, is mounted on an aluminum heat sink weighing 0.31 kg and reaches a temperature of 100°C in ambient air at 20°C under steady-state conditions. If the device is initially at 20°C, what temperature will it reach 5 min after the power is switched on?

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This question was answered on: Jul 11, 2017

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