Hobbies And Interests
Human Battery
The human battery requires two bits of metal (preferably copper and zinc), alligator clips, a multimeter and a human volunteer. After connecting each electrode to the two ends of the multimeter, the volunteer lays his left hand on one electrode and his right hand on the other. If done right, the multimeter will register an electric current. The teacher can then ask different students to act as batteries, allowing some to touch the electrodes first with wet hands and then with glove-covered hands, to show them how the slightly acidic sweat on their skin acts as a medium for the battery's chemical reaction.
Coin Battery
A coin battery consists of small pieces of absorbent paper soaked in salt water and a stack of nickels and pennies. The battery is basically a penny stacked on top of a nickel, with a piece of wet paper sandwiched in between; however, the current it produces is generally too low for a multimeter to detect. Stacking these nickel-paper-penny sandwiches on top of one another creates a series of batteries that will eventually generate enough current to power a small light bulb or a digital thermometer. Students must make sure that all layers are in contact with one another and that a nickel and a penny are on the battery's opposite ends.
Fruit or Vegetable Battery
Fruit and vegetable batteries are another common experiment for grade school students. Because the juices in fruits and vegetables contain plenty of ions, they make ideal battery electrolytes. For this experiment, students need copper and zinc electrodes -- such as a penny and a galvanized nail -- and a fruit or vegetable of their choice. Potatoes, lemons, and onions are among those most commonly used. A piece of magnesium would make a good substitute for zinc, but they are generally harder to find. A single fruit or vegetable battery can generate enough power to make a digital watch run.
Saltwater Battery
Saltwater batteries are ideal for experiments that require changes in battery configuration or electrodes, as they can be quickly modified. To build this type of battery, students need cups filled with salt water as well as electrodes of their choice. A cheap alternative for copper and zinc that would still work fairly well for a saltwater battery is a couple of tongue depressors wrapped in aluminum foil. Enough cups of salt water connected in series can charge a capacitor, power a simple circuit or set off a piezo buzzer.