The problems involved with making and breaking electrical contact with a moving coil should
be obvious (sparking and heat), especially if the shaft of the generator is revolving at high speed.
If the atmosphere surrounding the machine contains °ammable or explosive vapors, the practical
problems of spark-producing brush contacts are even greater. An AC generator (alternator) does
not require brushes and commutators to work, and so is immune to these problems experienced by
DC generators.