Did I understand this diagram correctly? How do you put a load on a positive wire?
A circuit requires a closed loop to operate. Therefore one could either disconnect the V+ or 0V line to the load and no current will flow through the load.
Transistor switching circuits come in two varieties.

&quot;High Side Switch&quot; , sits between v+ and load and disconnects V+

&quot;Low Side switch&quot; sits between load and 0V and disconnects 0V


You have a low side switch schematic, but there are also some other errors associated with it, so it is not so important to illustrate the concept.
From a purely electrical perspective and a basic load they are equivalent, for example, if your load is a heater coil or light bulb then it doesn't matter which side you switch.
There are secondary effects, in complex circuits there may be many things referenced to 0V, it could be considered a safety hazard to have the load energized to V+ . For example if the load is a heater coil, using a low side switch will leave the coil at V+ potential, a grounded technician with reference to 0V is therefore at risk electric shock when the switch is off.