The second finger (third digit) has the most literal meaning of all. Less commonly referred to as the long or tall finger, the digitus medius manus sits in the center of the hand, right between the digitus secondus manus and the ring finger. How the middle finger became an offensive gesture is another story altogether.
To see how the pump works, look at the drawing below. The pump consists of a small diameter pipe (called the piston) inserted into a larger diameter pipe (called the cylinder). The drawing shows the pump at two points during its operation. The top drawing shows air being drawn into the pipe by pulling out the piston. The bottom drawing shows air exiting the pipe when the piston is pushed back in. At the right end of the pipe is a commercially bought one-way valve.
Draw the electric field lines. Starting at the positive electrode on your diagram, draw a line to the negative electrode in such a way that the line always crosses an equipotential line at right angles. Draw 6-9 field lines through the region between the electrodes and the regions above and below their ends.