Lemon Lab:
Never in my wildest dreams did I think it was possible for a lemon to power a battery. It turns out this is possible through voltage which is similar to that of a mountain. Electrons go up and the protons go down the mountain creating charge! This makes sense after taking the lemons and after sticking a penny and a nail inside the lemon we were able to see the scientifically beautiful results.
The iPad is a staple in the education of an SI student nowadays. This is possible through the lithium-ion polymer batteries that iPads use. These batteries have a long battery life because of their high power density. When charging the iPad battery, the voltage increases in the first two hours and stays constant for the final two hours. The iPad charges to 80% in very quick fashion which is why the voltage greatly increases for the first two hours. But when it reaches 80% the voltage is constant hence the large charging period. The "mountain" is working a lot for the first two hours to charge the iPad and then works at a constant speed for the last two hours. I have much more respect for the people at apple that develop this stuff!
http://www.apple.com/batteries/
