26. What goes wrong when the capacitor is too small? In other words, what limit mentioned or implied in the problem is reached? How close together can you put the plates? The text has a relation for the amount of energy stored in a capacitor.
27. When the dielectric is removed from capacitor 2, what happens to the charge on the capacitor? Can it go anywhere? Do you have to pull on the dielectric to remove it, must you push on it to prevent it from flying outward , or does it come out freely and without acceleration? It is very hard to see which by analyzing forces, can you find out indirectly? Again, you need the text result for the energy stored in a capacitor.
28. This problem contains its own hints.
29. Now we put everything together. The capacitance depends on q and the potential difference, so you have to calculate q. If you had the reverse problem [given q, find V], how would you do it? What method, when it works, is the easiest way to find a potential difference?
| Last revised 1998/03/11 |