I never understood the concept of an electrical ground. And while working on my truck, I notice almost all of the fuses and switches have positive, negative, and ground. But if a tail lamp or bulb wire is touching ground, that can cause it to not work.
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Electricity wants to flow towards the earth. But in electrical circuits “earth” can be thought of as a reference point between the voltage and the point where the electric current will return. So it doesnt have to be actual ground but just the point where the current wants to return. The ground reference can change. For example, if barefoot you standing on wet earth touches the circuit, you are now the ground.
They call it ground, but since your car has rubber tires that obviously isn’t connected to the actual ground. The negative (usually) post on your battery is bolted to the frame and they call it ‘ground’ because it acts like a ground in a building. For example if you have a damaged wire, the grounded metal will allow the electrical current to flow from the damaged wire into the metal frame and back into the battery, completing the circuit (thus allowing the fuse to heat up and blow to protect your wiring from melting).
A ground in electronic devices is essentially a path through which electricity can flow should an accidental connection be made between the intended electric circuit and the case, frame, or other parts of the product that can carry electricity. The idea is that the accidental connection causes electricity to flow into the ground instead of into a person touching the device. In general, modern devices without a ground on the plug are designed with redundant insulation instead, to keep the exterior from becoming live.
Cars use DC voltage, with the negative side of the battery connected to the frame of the car as ground. TBH, I don’t recall any switches or fuses on cars that I’ve worked on having separate ground connections, though there are other devices that might. But it’s been a long time since I’ve worked on a car, so perhaps practices have changed.
Here’s an ELI5 answer. Put your head in a vise.
If you have it wide open and press your head against one side of it, but the other side is not touching, there is no force being applied. Tighten the vise, and you’ll feel force.
A ground is the side of the vise that does not move. It is a reference point that is constant, and used to measure how much force is being exerted by the side of the vise that moves.
In further detail- Wattage is the total amount of force applied in a specific time frame.
Voltage is the amount of pressure (imagine pounds/square inch)
Current is how quickly that force is being applied.
Your voltage X your current = your Wattage, or total power.
Ground is just a way of saying the same voltage as the environment. When you building a circuit, sometimes you want to compare the voltage on a particular output to “zero” volts, but that doesn’t actually exist in real life so you use the closest thing, which is the voltage of the surrounding environment. This also gives you an easy way to make sure parts of the device are always safe to touch, because you can connect them to the part of the circuit that is at zero volts, or “grounded”
An electrical ground is a return path for current to get back to its source.
It is important to understand the difference between chassis ground and earth ground. A chassis ground (like the one in your truck) is generally used for troubleshooting. Your negative and ground are the same thing. If you are measuring voltage anywhere on your truck you can find the positive wire and measure it against anywhere on the frame of your truck. So ground in this case is a reference point. An earth ground is a safety feature we see generally when we’re talking about AC circuits.
When a wire is bare and it touches ground it is the positive side of the circuit coming into contact with the negative side of the circuit prematurely. This is a short. Because the circuit has much less resistance you will likely bypass the device you’re trying to power and blow a fuse. Ohm’s law helps us here. For example a 12v supply (your truck battery) divided by 1 ohm resistance (your short circuit) equals a 12A flow. If your fuse is rated at less than 12A it will blow. If you decide to “fix” this problem by inserting a 15A fuse you will generate heat and possibly melt some wires.
Voltage is relative, you need a reference. Ground in a system is the point that all other voltages are relative to, its defined to be zero volts. Generally you want a big conductor so there are lots of electrons and it won’t change voltage significantly no matter what you do or where on it you measure.
For your home power grid, the ground wire and the neutral wire are referenced to Earth Ground by a long metal rod next to your house.
For your car there’s no physical earth connection but there is a big metal chunk that’ll do the job just fine, the chassis. In your car one terminal of the battery is tied to the chassis and the other provides power to other systems. This is handy because it means you only need to run 1 wire out to most systems because they can return the current through the metal of the car without needing a separate wire running all the way down the car.
In your phone there will still be a ground plane despite definitely not having a connection to earth ground. This is going to be a big layer of copper in the circuit board that is tied back to one terminal of the battery. Again, the big piece of metal keeps there from being much of a voltage difference between any two points on it.
electricity is flowing electrons, and they can’t flow one way because they’re electrically charged like magnets, so if they built up in one place they’d push away more from going that way.
so if they can’t go on a one-way trip, they need to go in a circuit, a loop, or to the earth because the earth is so huge it will never build up electrons and push any more away
the ground is the “common return path”, a route back to where they came from (or to earth) that lets them complete their trip.
if a wire “shorts to ground” by a bare wire touching something grounded, then, well, it’s just what it sounds like, their trip down the electrical path is cut short and they don’t go everywhere they were meant to go. Any components that are located in the circuit after the electrons take an unexpected off ramp won’t get any electron traffic.
In a circuit, electrons move from the negative to the positive, doing work along the way. In most circuit, there is a source element which the electrons start at the negative terminal of and flow through the circuit to reach the positive terminal, in most cases, this is a battery, Now, if the intended path breaks, those electrons are still going to try to get to the positive terminal of something, and when electrons go where they are not suppose to, bad things tend to happen. Usually fires. The ground terminal is there to provide a safe path electrons to go if that happens, connected to a large electrically positive reserve. In many circuits, this can be literally the ground, as the earth itself is mostly positive. In your car, the metal in the frame serves the same function. Now, if you attempt to connect an electrical device to ground instead of the usually terminals, the electrons will flow into the ground instead of into the device.
In digital electronics, the ground does the same thing, but it’s used in a different way, serving a hard 0/Off in the boolean logic.
If some short circuit happens then the electric current will flow to sensitive parts of the appliance or flow through you (dangerous) when you touch it.
Ground wires direct the stray current from the appliance to the ground without having it flow through your body or other sensitive parts of the appliance.
Since the stray current flowing to the ground is basically waste, it won’t power your appliance.
Think of it like your rainwater drain. Instead of flooding streets the drain directs the water away to a place where it is safely disposed of.
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