By Horsepower if you mean engine ouput ? If so these days it is often expressed in kilowatts rather than horsepower (1HP=0.746kW)
5
A watt is simply the SI unit for power, and the horsepower is the Imperial unit for power. Power is simply the rate of doing work, so there is no such thing as 'electrical' or any other, 'sort' of power. In Europe, a car's engine output power ('brake power') is expressed in kilowatts as the horsepower is considered obsolete.
no
Electrical power is also measured in Watts.
Horsepower is not a unit of mass.
joules & newtons
The definition of horsepower is a unit of power equal to 746 watts. Therefore, a cow has no horsepower.
watts, horsepower, tons of refrigeration, etc.
Motors are only rated in horsepower in North America, in most other countries, they are rated in watts. The reason for doing so, is that a motor's power is always expressed in terms of its output power -that is the maximum power it can supply to its mechanical load. If, as in North America, a mechanical load is expressed in horsepower, then so is the output of the motor; if, as elsewhere, a mechanical load is expressed in watts, then so is the output of the motor.Don't forget a horsepower is simply the Imperial unit for power, whereas the watt is the SI (metric) equivalent. 1 HP = 746 watts.
Horsepower
Horsepower
Hertz.