Final answer:
In a DC generator, the brushes are in direct contact with the commutator, ensuring the transition between electrical contacts as the rotor spins and a DC output is produced.
Step-by-step explanation:
In a DC generator, the brushes are in contact with the commutator. The brushes provide a conducting link between the rotating commutator, which is attached to the rotor, and the external electrical circuit. As the rotor spins, the commutator segments pass under the brushes, transitioning between electrical contacts. This arrangement allows the generator to produce a direct current (DC) output, by rectifying the alternating voltage induced in the rotor coils. The brushes are not in contact with the field poles, which provide the magnetic field necessary for the operation of the generator, nor are they in contact with the rotor directly; their sole contact is with the commutator.