|My Co-Op class|
The Toolman had helped me tape together four 9V batteries and connect them in a series. The DVD didn't give much instruction on this point, but it appeared they soldered the wires. We connected them with alligator clips I'd picked up at Radio Shack (where I also got a pack of LED lights). Here's the set-up...jab a fork into either end of a pickle. Use alligator clips to connect the battery pack to the forks ( I didn't want to use my nice forks, but it was easy to find junk forks at Goodwill). To "see" if current is flowing through the pickle, stick some of the LED lights in the top and see if they light up. It is helpful to use several lights in each piece of food. They only light if place in the right direction, and you can't tell by looking at them which way that is, so increasing the number of lights increases your chances that one is correct. Then you can turn the unlit one around.
In the DVD, Asa demonstrates a current flowing through a pickle, a candy bar, and a glob of mayonnaise. I told the students to bring a food item to class and we ended up with: a russet potato, a sweet potato, a yellow onion, a Twinkie, an apple, some string cheese, and a slice of French bread. Before each student took his or her turn, we'd vote on what we thought the outcome would be.