What happens to the capacity and efficiency of a pump as the force it works against increases?

As the force a pump works against increases, both its capacity and efficiency typically decrease. This phenomenon is primarily due to the increased load that the pump must overcome. When a pump has to work harder against greater resistance, it results in a less effective transfer of energy, which can lead to a reduction in the flow rate or volume of water being moved, thus decreasing the pump's capacity.

Additionally, the inefficiency arises because pumps are designed to operate most effectively at specific conditions. When the operating conditions deviate from those optimal conditions due to increased resistance or head, the energy consumption relative to work output increases, leading to decreased efficiency.

In summary, as the force increases, it creates a situation where the pump struggles to maintain its designed performance, resulting in diminished capacity and overall efficiency. This understanding is crucial for operators to ensure that pumps are used within their optimal range to maintain performance.