An electrically powered pump is used to pull water out of a well. In the course of an afternoon, the pump does 8.3 kJ of work lifting water out of a well?

An electrically powered pump is used to pull water out of a well. In the
course of an afternoon, the pump does 8.3 kJ of work lifting water out of a well.
It also heats up, and releases 300 J of heat to the environment before returning to
its original temperature. If there was no net change in the energy of the pump,
how much electrical energy was required?

2 Answers
May 9, 2016

Answer:

#8.6kJ#

Explanation:

In thermodynamics, you have the famous equation;
#Q=U+W#
Which is; #"Energy supply"="Internal energy"+"Work done by the system"#

The system heats up hence #U=300J#
Work is done by the system hence #W=8.3kJ#

Energy supply, #Q=8.6kJ#

May 9, 2016

Answer:

#8.6kJ#

Explanation:

Mechanical Work done by the pump#=8.3kJ#
Heat generated in the pump, due to internal resistance both electrical and friction#=300J#
Also given that change in energy of pump #DeltaE=0#

#:.# Total electrical energy was required#="Mechnical work done"+"Heat generated and lost"+Delta E#

Inserting giving values we get

Total electrical energy was required#=8.3+0.3+0=8.6kJ#