The CFM of a fan is ________ the rpm of the fan.

The CFM (Cubic Feet per Minute) of a fan is directly proportional to the RPM (Revolutions Per Minute) of the fan, meaning as the RPM increases, the CFM also increases. This relationship is fundamental because the primary function of a fan is to move air, and the speed at which the fan blades rotate directly influences the volume of air that is displaced in a given time frame.

A fan operating at higher RPM will spin its blades faster, thus enhancing the amount of air being pushed through the system, resulting in a higher CFM rating. This proportionality allows designers and engineers to estimate airflow based on the rotational speed of the fan, which is essential for various applications such as HVAC systems, where the correct airflow is crucial for maintaining comfort and efficiency. Understanding this relationship is key when sizing fans for specific environments or requirements, ensuring that adequate airflow is achieved with optimal energy consumption.

The other options do not accurately depict this relationship: indirect proportionality suggests an inverse relationship, which is not true in this case; stating that there is no relationship fails to acknowledge the clear link between RPM and CFM; and saying that it is simply affected by RPM overlooks the clear proportional nature of their relationship.