Does electricity always flow in a closed loop and why does current flow to ground?
In theory, you cannot get shocked and current will not go to ground if you touch one of the leads because the ground is not connected to the source which is the alternator.


That's correct but both in theory and in practice we have to remember about capacitance between the generator and ground and between the human body and ground.



Figure 1. Capacitance can close the loop in an isolated system.

In Figure 1 we can see that the effect of capacitance between the generator and ground could lead to a significant (mA) current flow.

In Europe we use isolation transformers for portable tools in the workplace.



Figure 2. A 110 V tool safety transformer with centre-tapped secondary.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 3. In the tool transformer the 110 V secondary centre-tap is deliberately grounded to provide a 55-0-55 output voltage.


The tool is powered from the two outer pins. This limits the output voltage to 55 V AC maximum in the event of a fault.
Having a definite ground point means that in the event of a single fault one of the output fuses will blow and this will alert the operator to the fault. Without this earthing feature one side could become grounded and if the operator were to come in contact with the other wire s/he would receive a 110 V AC shock.


You will find that many portable generators feature a 55-0-55 winding or transformer built in to provide this safety function. It's safety will depend on a proper grounding of the winding centre-tap.