@Brian DAgostino,
Obviously the power source negative/neutral terminal is connected to the earth/ground for a return path...
Later on experts found out that current actually flows in the opposite direction from the negative terminal to the appliance then to the positive terminal.
Even though conventional flow is now invalid, some teachers and text books still use conventional flow to explain the operations of semi-conductor components because diode schematic direction arrows point in the conventional flow direction making it easier to explain semi-conductor operations...