Insulate!
If I started to talk about insulation, what would be the first thing that comes to mind? A down coat? The pink stuff in the walls of your house? Something else? Actually, I won’t be talking about any of those things here. Within electrical engineering, insulation is sort of the less-glamorous sibling of all of the flashy electron goodness we normally talk about.
We normally don’t think about insulation but it’s critical to both how all of our electronics function as well as our own safety. The opposite of an insulator is a conductor. Conductors conduct electricity, insulators insulate electricity. The difference isn’t so clear cut though because technically speaking, everything can be a conductor…if the voltage is high enough. I’m sure I’ve mentioned this in relation to other topics before but I think it’ll be worthwhile to really dig into it specifically here.
In many previous articles, I’ve mentioned how voltage can be thought of as analogous to pressure in a water system. What creates the pressure in a water system though? Typically the pressure is created by some kind of gradient across which there is some difference in potential energy. Think of a water tower. Water is pumped high up into the tank at the top. While the water is sitting there, it has potential energy. If the pipe to the tank is opened, gravity will push the water down. Once the water dissipates at ground level, it has no more potential energy. As the water flows in the pipe, pressure will be exerted on the pipe walls, as well as at the end nozzle.
Electricity doesn’t work exactly the same way because it’s not a fluid, but the key element is the potential energy gradient. We refer to this gradient as voltage in electrical systems. The higher the gradient, the higher the pressure. In our water tower, say we had a valve at the bottom of the pipe. That valve is able to withstand and hold back some amount of pressure, but at some point, if the pressure became great enough, the valve would fail. There is always some amount of pressure where the valve would fail. It might be really, really high, but it does exist.
Electricity functions basically the same way. Insulators don’t allow electricity to flow, just like our water valve, but just like our water valve, if the pressure (voltage) becomes great enough, the valve (insulator) will fail. This property is something engineers pay very close attention to, in both design and safety aspects. A printed circuit board, for example, has lots of tiny wires placed very close to each other. Their functionality depends on the electricity being isolated to those wires and not jumping between wires. This doesn’t happen because the plastic substrate onto which the wires are etched is an insulator that doesn’t allow electricity to flow. Engineers may test circuit board designs by applying varying amounts of voltage to see where the insulation breakdown occurs to make sure that under normal operating voltages, the circuit will function normally.
Obviously there are safety aspects to this as well. If you were working near open conductors, you might want gloves that would sufficiently insulate your hands from the electricity. These kinds of properties are known for all sorts of materials and conditions. Some materials (rubber, glass, air, Teflon, diamonds, wood) are very good insulators for normal uses. Some materials are just ok insulators (graphite, sea water), but then you start to switch back into things we commonly refer to as conductors such as copper, iron, tungsten, etc. Obviously for some voltages there won’t be a practical insulator available. Sometimes instead of trying to insulate against the full force of some voltage, engineers will channel the electricity elsewhere. Examples of this are lightning rods and faraday cages.
As with so many things, it’s interesting to find that electricity is not merely insulators and conductors but the entire gradient of those materials.