Goal: Reason regarding capacitors
Source: 283-545 Adding capacitors in parallel
A capacitor having, C1, is connected to a battery until
charged, then disconnected from the battery. A second capacitor,
C2, is connected in parallel to the first capacitor. Which
statements below are true?

- Charge on C1 decreases.
- Total charge on C1 and C2 is the same as the original Q.
- The total energy stored in both capacitors is the same as the
original U stored in C1. - The potential (Voltage) across C1 decreases.
- All of the above.
- Only 1, 2, and 3 are true.
- Only 1, 2, and 4 are true.
Commentary:
Answer
(7) Statement #3 is the hardest for students to reason about. This is
most easily decided as incorrect if the two capacitors are taken as
equal.