Question

An electronic device dissipating 25 W has a mass of 20 g and a specific heat of 850 J/kg·0K. The device is lightly used, and it is on for 5 min and then off for several hours, during which it cools to the ambient temperature of 250C. Let the mass of heat sink vary from 0 to 1 kg. Plot the maximum temperature against the mass of heat sink, and discuss the results. U

Answer 1

Step-by-step explanation:

FIrst let c be the specific heat, now we need the heat that the device is able to provide:

so it is turned on for 5 minutes (300 seconds) with 25 Watts

`Q = Power*time = (25)*(300) = 7500J`

Now heat is equal to the change in internal energy, where we will use the remaining terms.

Now we continue

`Q = \Delta U = M*C(\Delta T)`

where
`\Delta T` is the change of temperature (
`\Delta T = T_(final) - T_(initial)` )

now
`Q = \Delta U = M*C*(T_(final) - T_(initial))`

We solve
`T_(final) = (Q)/(M*C) +T_(initial)`

now we just plot it for different values of M using any software..

please find attached the plot of the temperature.

The result indicates that as the mass increases it is harder for the system to reach higher final temperatures.