Concept explainers
The temperature of the device at the end of the 5-min operating period with and without the heat sink.
Explanation of Solution
Given:
The rate of electrical work to be done into the system
The mass of the electronic device
The specific heat of constant pressure for electronic device
The change in time
The initial temperature of the system
Calculation:
Write the expression for the energy balance equation.
Here, the total energy entering the system is
Simplify Equation (I) and write energy balance electrical device without heat sink.
Here, the electrical work to be done into the system is
Rewrite the Equation (II) into per unit time.
Thus, the temperature of the device at the end of the 5-min operating period without the heat sink is
Simplify Equation (I) and write energy balance electrical device with heat sink.
Here, the electrical work to be done into the system is
Rewrite the Equation (II) into per unit time.
From the Table A-3(b), “Properties of common liquids, solids, and foods”, obtain the value of specific heat of constant pressure for aluminium at 300 K temperature is
Substitute
Thus, the temperature of the device at the end of the 5-min operating period with the heat sink is
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Chapter 5 Solutions
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