Final answer:
The field of a DC generator is established when replacing a generator to provide the necessary magnetic field for operation. This process involves rotating wire loops within a magnetic field to produce DC, which can be pulsed or smoothed out with more elaborate arrangements of coils and split rings. The construction of generators and motors shares similarities.
Step-by-step explanation:
Field Excitation in DC Generators
When replacing a DC generator, the field of the generator is normally accomplished, which refers to the way the magnetic field is established in the machine. DC generators contain wire loops in a magnetic field, and these loops are forced to rotate by an external agent. This mechanical energy forces the loops to rotate within the magnetic field, thus inducing an electromotive force (emf).
The induction of emf in a DC generator can lead to the production of pulsed DC or smoother DC through more complex arrangements involving multiple coils and split rings. Often, electronic means are preferred over mechanical means to achieve ripple-free DC. The construction of a generator is very similar to that of a motor, highlighting a fundamental symmetry between these two types of machines.
It is important to note that the peak emf generated by a DC generator, which is directly proportional to the number of coils (N), the area of the coils (A), the strength of the magnetic field (B), and the angular velocity (w), can be expressed mathematically as 0 = NBAw. This implies that modifying any of these variables will impact the output voltage and performance of the generator.
Lastly, a generator is generally a device that converts other sources of power into electrical energy. It is not powered by electricity nor typically operated by hand, although hand-cranked generators do exist.