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Test Bank Ch.2

# Test Bank Ch.2 - Chapter 2 Energy Energy Transfer and...

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Multiple-Choice Test Problems Chapter 2: Energy, Energy Transfer, and General Energy Analysis Çengel/Boles - Thermodynamics: An Engineering Approach, 5 th Edition (Numerical values for solutions can be obtained by copying the EES solutions given and pasting them on a blank EES screen, and pressing the Solve command. Similar problems and their solutions can be obtained easily by modifying numerical values.) Chap2-1 Heating by Resistance Heater A 1.5-kW electric resistance heater in a room is turned on and kept on for 20 min. The amount of energy transferred to the room by the heater is (a) 1.5 kJ (b) 60 kJ (c) 750 kJ (d) 1800 kJ (e) 3600 kJ Answer (d) 1800 kJ Solution Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. We= 1.5 "kJ/s" time=20*60 "s" E_total=We*time "kJ" “Some Wrong Solutions with Common Mistakes:” W1_Etotal=We*time/60 "using minutes instead of s" W2_Etotal=We "ignoring time" Chap2-2 Heat Supplied by Vacuum Cleaner A 200 W vacuum cleaner is powered by an electric motor whose efficiency is 70%. (Note that the electric

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