So I bought a motorcycle that doesn’t work, and I’m trying to fix it up. I’m pretty new to electrical work, and having trouble with the concept of the ground. On my bike, the electrical components are grounded to the steel frame, and the negative battery terminal is also grounded to the frame.. so is the frame basically a conductor back to the negative terminal? Why is it not dangerous to be exposed like that unlike the insulated wires??
In general the concept of ground is a little hazy for me.
Thanks
In: Physics
Ground in vehicles and ground in your house serve a different purpose
Things labeled “ground” are mostly so there’s an agreed upon reference for 0V in the system. Just about every system has a “ground” terminal somewhere just so we can agree what all voltages should be measured to
The ground pin on outlets in your home is a *safety* ground, it is not supposed to carry currents under normal circumstances, its just there to make sure that parts of the device you can touch remain safe at all times. Back in your breaker panel all the ground wires and neutral wires and tied together and hooked to a long metal rod that goes into the dirt, this is the actual ground reference, the ground in all your outlets is just for safety
For vehicles and other relatively low voltage DC applications, you don’t need a safety ground. There isn’t enough voltage available for anything really shocking to happen so ground is simple the reference 0V point for everything in the system. In general the negative terminal of the battery is connected to the body of the vehicle so we can define the negative terminal as 0V and the positive as +12V to keep things simple.
Having the frame tied to ground also greatly simplifies wiring of the vehicle as you only have to route a single +12V wire to many systems as they can use the bolts that connect them to the frame to provide their return path so you have half as many power wires running around which is a lot cleaner and cheaper.
Since the frame of the vehicle is all nice conductive metal it has a very low resistance, so while there may be a fair amount of current running through it there is almost no voltage difference across it so every point on it is very close to that 0V reference of the – terminal. Since there’s basically no voltage across it there’s no way to generate a potential difference across you by touching two points on the frame so its safe to make contact with.
Latest Answers