Hand battery

1. Content

The exhibition items consist of an ammeter, a metal rod device, and a background plate. There are four different materials of metal rods designed, namely (tentatively) copper, aluminum, iron, and zinc, connected to both sides of the ammeter. When visitors come into contact with the metal rods with slightly sweaty wet hands, an electrochemical reaction occurs, resulting in a small current. However, when both hands do not hold the metal rods, no current is generated, and the ammeter displays 0.

2. Principle

A battery formed by inserting different metal sheets into an electrolyte aqueous solution is commonly known as a voltaic battery. Because zinc has stronger reducibility than copper, it is more likely to lose electrons and act as the negative electrode in batteries. And when cations gain electrons on the surface of copper, the copper plate becomes the positive electrode. The principle of a primary battery is actually a spontaneous oxidation-reduction reaction.

As long as two different metals are used as electrodes and inserted into the electrolyte, output current can be obtained. Due to the salt content in the sweat of our palms, a very simple handheld battery is formed when our hands are placed on two different metal rods on the left and right. Similarly, inserting aluminum and zinc sheets into sulfuric acid solution will also generate current in the circuit, which is a common chemical battery. According to the same principle, it is also possible to make Apple batteries, potato batteries, and so on.

3. Purpose

The exhibition items use the form of electromechanical interaction to enable visitors to understand scientific knowledge related to human electrochemical reactions through the interactive experience of touching metal rods of different materials.