Two large parallel sheets of charge are separated by a distance d, small compared to the size of the sheets. The distance d is small enough that the sheets can be treated as if they were infinite in extent. The amount of charge per unit area in the sheets are +σ and -σ respectively. A conducting plate of width d/2 is slid in between the two plates as shown in the figure at the right.

Select which of the graphs below could be appropriate to give a graph of each of the following quantities. If more than one answer works, give them all. If none works, write N.

1. the electric field between the plates before the metal plate was inserted.
2. the electrostatic potential between the plates before the metal plate was inserted.
3. the electric field between the plates after the metal plate was inserted.
4. the electrostatic potential between the plates after the metal plate was inserted.