A _series_ motor has a powerful starting torque, and adjusts its speed to the load. It is used almost altogether in street cars. It can be used in stump pulling, or derrick work, such as using a hay fork. It must always be operated under load, otherwise, it would increase in speed until it tore itself to pieces through mechanical strain. The ingenious farmer who puts together an electric plow, with the mains following behind on a reel, will use a series motor. A _shunt_ motor should be used in all situations where a fairly uniform speed under load is required, such as separating, in milking machines, running a lathe, an ensilage cutter, vacuum cleaners, grinders, etc. The _compound_ motor has the characteristics of the series and shunt motors, giving an increased starting torque, and a more nearly constant speed under varying loads than the shunt motor, since the latter drops off slightly in speed with increasing load. _Flexible Power_ An electric motor is an extremely satisfactory form of power because it is so flexible. Thus, one may use a five horsepower motor for a one horsepower task, and the motor will use only one electrical horsepower in current--just enough to overcome the task imposed on it. For this reason, a large-sized motor may be used for any operation, from one requiring small power, up to its full capacity. It will take an overload, the same as a dynamo. In other words it is "eager" for any task imposed on it; therefore it must be protected by fuses, or it will consume itself, if too big an overload is imposed on it. A one horsepower shunt or compound motor is very serviceable for routine farm operations, such as operating the separator, the churn, the milking machine, grinder, pump, and other small power jobs. Motors of 1/4 horsepower are handy in the kitchen, for grinding knives, polishing silver, etc., and can be used also for vacuum cleaners, and running the sewing machine. For the larger operations, motors will vary from three horsepower for cutting ensilage, to fifteen horsepower for threshing. They can be mounted on trucks and conveyed from one point to another, being fed current from the mains by means of suitable wires wound on reels.