I was hoping the load line of the resistor would show him how
the LED responds to different amounts of current.
Polymorph made it clearer than I could.
The voltage of his second chart doesn't go to 5 volts. I'm sure you can
print the chart out and draw a line to the 5v or even 9v is needed.
One point to note. The larger the voltage drop, the smaller the difference
in current is.
Draw some load lines, starting at different voltages, say 3,3v instead of 5v
for the source.
Dwight