Mechanical load

Load, in mechanics, is the external mechanical resistance against which a machine, such as a motor or engine, acts. The load can often be expressed as a curve of force versus speed.

For instance, a given car traveling on a road of a given slope presents a load which the engine must act against. Because air resistance increases with speed, the motor must put out more torque at a higher speed in order to maintain the speed. By shifting to a higher gear, one may be able to meet the requirement with a higher torque and a lower engine speed, whereas shifting to a lower gear has the opposite effect. Accelerating increases the load, whereas decelerating decreases the load.

Similarly, the load on a pump depends on the head against which the pump is pumping, and on the size of the pump.

Similar considerations apply to a fan. See Affinity laws.

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