Nine Volt Daisy Chain

My mother used to be a photographer and was always eating through nine volt batteries. Back in the days of 9mm film, cameras had a port on the top where the operator could attach a flash. While the mechanical camera had no need for a battery, its electrical counterpart certainly did.

After a photo shoot the flash would grow dim and the battery would need to be changed. Perhaps the dimming of the light was noticeable by everyone, or perhaps it was only perceptible to the photographer, but by the time she passed the battery along to her teenage son it still had plenty of charge. Or, at least enough to give me a painful bite when I pressed it against my tongue.

Sometimes she gave me a single battery at a time. Other times, like this fateful day, she gave me a box of 18.

Nine volts, if you're unfamiliar, have two terminals. The positive terminal is smaller than the negative. A battery will securely fasten to a plug as the large terminal squeezes around a small terminal. One feature—the true purpose of which still eludes me—is that the plug for a nine volt battery is shaped exactly like the terminals of the nine volt battery, only in reverse: the small battery terminal fits into a large terminal on the plug, and the small terminal on the plug fits into the large terminal on the battery. By virtue of this simple, symmetrical plug, one can attach two nine volts to each other. This coupling of two batteries results in a heated battle, and within an hour both batteries are dead.

Even more notable is that one can rotate each battery by 180 degrees, and plug one side of a battery into another—again, positive to negative. Then attach another battery onto the second. And a fourth onto the third. Before long I had daisy-chained 18 nine volts together. This series of batteries totalled 172 volts.

I wasn't very old at the time but I did have enough forethought to avoid touching both ends of the daisy chain (the already-painful wall outlet supplies 120 volts, after all). I went through my box of parts and attached wires with insulated alligator clips to the end terminals. Now I just needed something to electrocute…

At first I attached the clips to various circuit components. Resistors, intended to impede the flow of electricity smoldered in my wake. Light Emitting Diodes would flash for a moment before burning out forever. Capacitors—little blue cylinders meant to store electricity—were the most exciting, especially tiny ones which expect a few volts.

"Fffffrrrreeeeeeeeiiiiiii… Pop, Tak!" A capacitor launched from my hands like a rocket and bounced off the ceiling. A few more followed. For science.

Around this point I remembered chemistry class. Water is made of hydrogen and oxygen. A single nine volt battery on my wet tongue would tingle. Why was that? Could it be?

I dug through my box again and discovered a plastic tank which I filled with water. I dipped the first clip into the water and grazed the water's surface with the second. The water fizzled and produced bubbles. Could this be the separation of hydrogen and oxygen?

After a few experiments the alligator clips were charred. I needed to increase the surface area to prevent the metal from corroding. I attached a key to one of the clips and put that in the bottom of the water. I attached a paper clip to the second. The water fizzled some more, this time without damaging the alligator clips.

I needed to find out if the bubbles were really hydrogen and oxygen and not just steam. I procured a test tube (I believe all teenagers in the nineties had a chemistry set) and submerged it in the tank. A sealed container can be filled with water and be lifted above the surface of a larger body of water without emptying—as long as the opening remains submerged. I used this knowledge to keep the test tube full of water while upside down.

I stuck the paper clip into the tube and dropped the key in the tank. The bubbles returned and collected at the highest point of the tube. A couple centimeters of gas formed during the next several minutes.

It was finally time to see if I had successfully separated water, which I later learned was called electrolysis, or if I had merely boiled water. I gently released the water from the tube, lit a lighter, and held it below the tube. I knew oxygen and hydrogen were both flammable and that something would happen… Alas, the disappointed flame wavered in the still air of my childhood home.

Wait, of course! Both hydrogen and oxygen are lighter than air. I would have to "dump" the gas out.

With the lighter still lit, I slowly turned the tube over, imagining the invisible meniscus between the pure gasses and air, as if the tube contained gravity-defying fluid. Once the tube was almost flat, and with the flame of the lighter against the opening, my teenage experiment finally paid off.

The gas exploded and engulfed my forearm in flame.

The straight and white hairs which once adorned my arm were now blackened and curled. A non-pyro, or otherwise responsible person, might have been alarmed. Yet the flames were short lived and brought little pain.

The smell of burning hair was dwarfed by excitement. The potentially-dangerous experiment helped kindle my curiosity and problem-solving skills. A discarded box of batteries provided a teenager with hours of education.

Thomas has contributed to dozens of enterprise Node.js services and has worked for a company dedicated to securing Node.js. He has spoken at several conferences on Node.js and JavaScript and is an O'Reilly published author.