A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The l
ID: 1009260 • Letter: A
Question
A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The lightbulb is turned on for 2.0×102 hour, and the assembly expands from an initial volume of 0.90 L to a final volume of 5.92 L against an external pressure of 1.0 atm.
Use the wattage of the lightbulb and the time it is on to calculate q in joules (assume that the cylinder and lightbulb assembly is the system and assume two significant figures).
Express your answer using two significant figures.
Calculate w.
Express your answer using two significant figures.
Explanation / Answer
power = work done / time taken ; 100 = work done/2*0.60*60 ; 72*100= work done ; work done by bulb= 7200 Wsecond = 7200Joule = 7.2 Kj;
Work done by the system = external pressure*volume change = 1*5.02 = 5.02L-Atm = 5.02*101.3 Joule = 508.6766 Joule. = 0.51 Kj
Q= 7.2-0.51 = 6.69Kj = 6.7 Kj
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