I just started reading a book on electronics and currently reading some concepts of earth ground. I came across a section that mentions practices about grounding as follows:
The ground terminal of the supply is tied to case of the instrument, which in turn is wired to the mains earth ground system. A common mistake for a novice to make is to attempt to power a load, such as a lamp, using the positive and ground terminals of the supply. This, however, doesn't complete a current return path to the energy source (supply), so no current will flow from the source; hence, the load current will be zero. The correct procedure, of course, is to either connect the load between the positive and negative terminals directly, thus creating a floating load, or using a jumper wire between ground and negative supply, create a grounded load.
Quote from Chapter 2, Theory of Practical Electronics for Inventors 3rd Edition by Paul Scherz
My question is:
If the circuit doesn't complete just using positive and ground terminals of the supply, how does it complete then in the case when the
ground is actually used correctly (in case of a accidental shock etc.)?
When the hot wire comes in contact with the chasis, the electrons flow from the less resistive path (instead of passing from the body) to the ground. Why can't they flow then when one end is connected to a positive terminal and the other to a ground terminal?