To answer the first question we imagine placing a + charge at
Point X.
The center charge will be repelled by the charge on the left and
attracted to the charge on the right. The center charge would
move toward the right.
The electric field arrow shows the direction of the force on the
center charge. The electric field arrow should point toward the
right.
The ground can be either negatively or positively charged.
If the ground were negatively charged the positive charge would be
attracted to the ground and the negative charge repelled
and pushed upward. That's not what is happening. So the
ground must be positively charged.
The positive charge is creating the
force that causes the positive charge to move upward. So that too
must be direction that the electric field arrow is pointing.
