A closed, well-insulated tank contains 0.15 kg of liquid water. The tank base is

Question

A closed, well-insulated tank contains 0.15 kg of liquid water. The tank base is a copper plate of mass 0.25 kg that acts as a heater by using an imbedded resistor as seen in the figure. Initially, the tank and its contents are at 30 C. The contents of the tank are heated during a process in which the resistor draws a linearly increasing current from 0 to 20 A over 2 minutes with a constant voltage of 12 V. The system is then allowed to come to equilibrium with now fruther heating. Determine the final temperature of the water. Use the incompressible substance model for the water and the copper with specific heats of c of the copper = 0.385 kJ/(kg x K) and the c of the water= 4.179 kJ/(kg x K). Neglect changes in the kinetic and potential energy and the mass of the tank walls.

Explanation / Answer

1 Both the water and the copper block are incompressible substances with constant specific heats at room temperature. 2 The system is stationary and thus the kinetic and potential energies are negligible. 3 The tank is well-insulated and thus there is no heat transfer.

Properties The density and specific heat of water at 25

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