Electronics Safety Lesson: Small Voltages Can Hurt You
When you work with electronic circuits, you work with electricity. Most electronics projects are low voltage – 6-9 volts. However, it's possible to injure yourself with voltages even as low as six volts.
For instance, if you accidentally create a short circuit between the two poles of a battery, a lot of current will flow very fast. This will very likely cause the wire connecting the two ends of the battery to get very hot, and the battery itself may also heat up. The heat may be enough to inflict a nasty burn.
If the racing current goes unchecked, there's also the possibility that the battery will explode. Trust me; you don't want to be nearby if that happens. You really don't want to make a trip to the emergency room to have fragments of an exploded battery removed from your eyes.
As a result of this danger, you should take the following precautions when working with the battery-powered circuits:
Don't connect power to the circuit until the circuit is completely finished and you've reviewed your work to ensure that everything is connected properly.
Don't leave your circuits unattended when they're connected to power. Always remove the batteries before you walk away from your workbench.
Periodically touch the batteries with your finger to make sure they aren't hot. If they're getting warm, remove the batteries and recheck your circuit to make sure you haven't made a wiring mistake.
If you smell anything burning, remove the batteries and recheck your circuit.
Always wear protective eyewear to protect yourself against exploding batteries. (Under the right circumstances, other components can explode as well!)