A metal rod driven into the earth with a wire attached to it. This, or something like this, is the lowest electrical point in your home's AC system. Grounds like these are installed mostly for safety and are required by law in nearly every country.
Power coming into your home is typically fed by two, or three wires from a transformer on the utility pole. These wires haven't any connection to ground. Heres what the system looks likje.
Not everything in our homes uses ground and - and this is important to understand - ground is not used to conduct electricity. Don't try this at home, but you could disconnect ground from Earth and little in your home would change, everything functioning as it should. All the power your home uses runs through the two or three incoming AC wires, not ground.
Ground is included mostly as a safety valve for us humans and a sink for unwanted noise for our audio equipment. Problem is, when we use ground to lower noise in our audio system–as in yesterday's black hole example–the hole we're sending our noise to is more gray than black. In other words, in a crowded community of homes and buildings, all that noise we're throwing into Earth becomes the equivalent of a toxic waste dump. And to make matters worse, ground's effectiveness changes with the weather; worse in summer, better in the wetter months of winter and spring.
For now, let's start understanding how we deal with grounds inside the equipment we own, then we'll move on to more grounded subjects. (I couldn't resist the double puns here).
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