electron flow?

Discussion in 'General Electronics Chat' started by tgower, Jun 12, 2011.

  1. tgower

    Thread Starter New Member

    Jun 12, 2011
    I work on automotive electrical systems and was taught that electron flow goes from neg to pos. Was taught that current flow is the same everywhere in a series circuit.Was wondering why is a circuit fused on the power side only? If electrons flow upthrough the ground side to the load why does the ground side not have to be insulated and the power side does? Any help would be greatly appreciated. T Gower
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    Since it's a circuit, a path for electrons, it can be interrupted at any point. Since car designers have arbitrarily made the frame and body common with the negative pole of the battery, it makes sense to fuse the uncommon part of the circuit, the positive distribution system.

    As previously stated, the frame and body are all at a common potential or voltage. If you insulate them, you're insulating them from themselves which is clearly pointless. In practice, all points of the electrical system that are above the level of ground are insulated.

    A series circuit has the same current flowing through all nodes of the circuit but the voltage is divided amongst the various components of the circuit. If any of these voltages contact ground or any other voltage through a direct short or some other low resistance, excess current will flow causing damage to circuit components, hopefully a fuse.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    Circuits are fused on the live side because a blown fuse on the ground side could leave the whole circuit "hot" with respect to ground: a dangerous situation.

    The fact that electrons flow from the negative side of the circuit is not really relevant to fusing. The negative side may be grounded in a DC circuit, but of course in AC the neutral line is only negative for half of the time. What is important is that the blown fuse leaves the circuit safe.

    Another point is that a fuse in the live side is likely to blow if there is a short-circuit to ground, whereas a fuse in the ground side would be bypassed by such a fault.
  4. Pencil

    Active Member

    Dec 8, 2009
    Maybe this will clear up some confusion.

    You only need to keep "the ground side" from touching "the power side".
    They are not being protected from the outside world, only from each other.
    Either one or both could be insulated, but it is easier to coat wire, make
    plugs of plastic, etc. than it would to coat the body/frame with insulating
  5. tgower

    Thread Starter New Member

    Jun 12, 2011
    Thanks to everyone for your help.T Gower
  6. SgtWookie


    Jul 17, 2007
    Just a side note...

    Up until sometime in the 50's for US-made autos and mid-60's for English autos, many of the electrical systems were positive ground (or positive earth, for you UK'ers and downunders). Eventually, negative ground won out as the standard; seems that some claim the positive ground caused accelerated body corrosion.