Was it necessary for the capacitor to be completely discharged at the final position?
If it
was not, what implications does this have for your experiment?
What is more
important, the total energy the capacitor is able to store, or the amount of energy the
capacitor transfers?
Is there a way you can visually determine that the capacitor is no longer transferring
energy to the mass?
What are the obvious changes to your system when energy is no
longer being supplied to the mass from the capacitor?
What are the uncertainties associated with your measurement?
Try to think of any
possible sources of uncertainty and quantify them.
A
NALYSIS
Calculate the initial energy of the mass.
Calculate the final energy of the mass.
Calculate the initial energy of the capacitor.
Calculate the final energy of the capacitor.
Combine the quantities you decided to be energy input and output to determine the
efficiency of the electric motor.
What are the implications if this number is equal to
one?
What if it is less than one?
Greater than one?
C
ONCLUSION
Did your results match your predictions?
Explain any differences.
How efficient is the electric motor?
89

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CHECK YOUR UNDERSTANDING
LAB 3: ENERGY AND CAPACITORS
For each of the arrangements of identical capacitors shown below:
1)
Rank them in terms of the amount of time they can light a light bulb.
Assume that the leads
shown have been connected to a 6 Volt battery and then removed from the battery and connected
to a light bulb.
2)
Calculate the potential difference between the terminals of each capacitor.
Assume that the leads
shown have been connected to a 6 Volt battery and that the capacitance of each capacitor is 10
µ
F.
3)
Calculate the amount of energy stored in each capacitor and the total energy stored in each
arrangement of capacitors.
Assume that the leads shown have been connected to a 6 Volt battery
and that the capacitance of each capacitor is 10
µ
F.
90