currentdcsafetyswitches
According to the research I've done, it is safer to place a switch on the positive side of a voltage source:
This only makes sense to me visualizing the circuit using conventional current (counter clockwise). When visualizing it in electron flow (clockwise), the opposite seems true. I think this stems from my use of the "water analogy."
Why does a switch go on the positive side of a voltage source?
I think you may actually need a bridge rectifier - it converts any polarity DC (or cyclic ac) into the same polarity: -
You can buy them as one lump with 4 leads or make them from individual diodes - make sure the voltage rating on the diodes is high though - I'd choose at least 1000V rated diodes because telephone lines do have a tendency to get induced voltages from nearby lightning strikes.
Electrons flow out one side (the negative one) and come back in from the other (the positive one). Current is not associated with electron accumulation, but with electron flow. The point of the battery is pushing electrons from the positive to the negative terminal: this pushing requires energy, that is chemically kept in the battery, used to push the electrons that then release it when they go through your circuit.
The negative sight might be or not ground. Ground is a word that is used to refer to a circuit particular node, sometimes connected to ground. You measure all voltages with respect to this node, so it is the zero voltage node. I understand you might think that electrons might escape if ground is connected to the negative terminal of the battery but that is not possible since they must go back in the battery because no net charge accumulation is allowed. If an electron pushed by the battery happens to escape through ground, another one will come from ground, make it through your circuit and then back in the battery.
Best Answer
In theory there is no difference, but practically there is because of how most engineers use "ground".
The problem is how sure are you that you truely are opening all paths for electricity to flow? If "circuit ground" is tied to the actual ground, something which happens to be resting on the ground may form a closed loop.
simulate this circuit – Schematic created using CircuitLab
This is common in "mains" electricity (i.e. the wall outlets), so if SW1 is closed, Joe is having a bad day. SW2 doesn't matter, and it doesn't matter if V1 is positive or negative.
Another common example is when you connect "ground" to a metallic chassis, which is common in the automotive world. The circuit for this looks similar to the one above. If you want to use a low-side switch, you had better make sure you don't have any metal contact with the body of the car or anything electrically connected to the body.