'Electrical drives' is a general term that is commonly used to describe both DC and AC excited motors that provide continuous rotary motion, whilst 'electrical actuators' provide linear or angular displacement. Both are widely used in a variety of practical engineering systems, including machine  tools,  robots and  aerospace systems. Other alternatives may use hydraulic or  pneumatic  principles  to achieve    similar objectives, but  the electrical  systems are    often  favoured because of the ease of control (especially using increasingly sophisticated computer based control   systems)  and  ease of installation and transmission of energy compared to mechanical    alternatives (requiring pipe-work, belts, rotating shafts etc). These, for example, are the motivations for increasing use of electrical systems in cars and 'the more-electric aircraft'.

The key to the energy conversion process is the 'Lorentz force' which is the force experienced    by    a    current    carrying conductor in a magnetic field. Although there are strong parallels with electrostatic forces (i.e. the force produced on a body carrying a static charge in an electric field), almost all drives and actuators rely on electromagnetic forces.