Final answer:
In physics, knobs or switches on modules control the amount of a physical quantity such as electrical current, light, or other types of energy that passes through a system, akin to changing a hula hoop's angle in a river which affects the water flow through it.
Step-by-step explanation:
The question you've asked is related to the concept of flux in physics. Modules, like the ones mentioned in your question, are configurations that could be in electronic devices or systems which manipulate physical quantities such as electrical current, light, or other types of energy. The knobs or switches on these modules allow you to adjust parameters that affect the amount of a physical quantity that passes through the system. In the case of the hula hoop analogy, as you change the angle of the hoop relative to the direction of the river's current, more or less water flows through. This is similar to how you might use a knob to adjust the amount of electrical current through a circuit, or how the amount of sunlight hitting a solar panel can be influenced by its orientation.
The control that knobs or switches provide could be compared to adjusting the strength of the current or the size of the hoop in the analogy, affecting how much of a particular quantity such as energy or light is being allowed to pass through or interact with the module. Whether you're thinking about a physical science context like a solar panel or an electronic device, the fundamental idea is that knobs or switches regulate the level of interaction with a particular flow or flux through the system.