Test the conduction of electricity through various fruits and vegetables.
Vegetables that conduct electricity
Potatoes, onions and tomatoes are all good vegetable conductors. Tomatoes are most likely the best vegetable conductor since they have the highest acidity level.
Fruits that conduct electricity
Some good fruit electricity conductors are apples, grapefruit, oranges, lemons and limes. The citrus fruits will be excellent conductors due, again, to the high acidity level. Acidic or Citrus fruits are best to conduct or even generate electricity. Acid in the fruits reacts with water and generates Hydrogen which is in ionic form and is positively charged (it lacks electrons).