Commercial batteries, apart from their normal electrolyte, contain chemicals with an affinity for hydrogen, which combine with the hydrogen before it can polarize the electrodes. Label the battery voltage and the resistance light bulb. If you place a strip of copper and a strip of zinc in contact with each other, many electrons pass from the zinc to the copper.
Many fruits and vegetables contain juices rich in ions and are therefore good electrical conductors. Check out the on the science behind this powerfully delicious snack. Otherwise, you can find the materials for a potato clock in any hardware store.
Have students complete the activity again using an electrolyte solution, such as salt water or vinegar. It's not enough power to shock you, but the potato can run a small digital clock.
They work best if you first roll them on a table top, which breaks down the cells inside so more juice flows through the fruit current.