Goal: reason and link electrical quantities
Source: 283-Del C, E, U, etc. – cstV
Two
parallel conducting plates form a capacitor. With a metal cylinder of
length half the plate separation inserted between the plates, it is
connected to a battery with potential ΔV. The cylinder is now removed.
Which of the quantities C, ΔV, Q, E, and U change?
- C, E, and U only
- Q and U only
- C and U only
- E and U only
- Q, ΔV, and U only
- ΔV and E only
- C and Q only
- None of the above
Commentary:
Answer
(8) Since ΔV does not change, E must because the distance between
plates doubles. If E changes, so must Q. If Q changes, so must C.
Finally, that U chages can be seen in a variety of ways.
There are many good follow up questions, such as: How would the
quantities change if the cylinder was made of a dielectric material?