(a) coils.
(b) coil sides.
(c) conductors.
(d) turns.
Answer: (a) coils.
Explanation:
CONCEPT: Commutator Segments
- A commutator is
a mechanical rectifier used in DC machines.
- Its
primary function is to:
- Convert
the internally induced AC in the armature into DC at
the terminals.
- The
commutator consists of:
- Copper
segments
- Insulated
from each other (by mica)
- Insulated
from the armature shaft
Connection Between Coils and Commutator Segments
- In a
standard DC armature winding:
- Each
armature coil is connected to one commutator segment
- Specifically:
- One
end of a coil is connected to a commutator segment
- The
other end is connected to the adjacent segment
- Thus,
each commutator segment represents the junction between two
adjacent coils.
Key Relationship
- Therefore:
- For
example:
- If
the armature has 72 coils
- The
commutator will have 72 segments
Why This Is Important
- A
larger number of coils and commutator segments:
- Increases
the number of overlapping EMFs
- Produces
a smoother DC output
- This
reduces:
- Voltage
ripple
- Sparking
at brushes
Additional Important Points
- The
purpose of the commutator is to rectify the AC waveform generated
in the armature.
- Carbon
or graphite brushes collect current from the commutator and
supply it to the external circuit.
- Armature
coils are insulated from:
- Each
other
- The
armature core
- Similarly,
commutator segments are insulated from:
- Each
other
- The
armature shaft
FINAL CONCLUSION
- In
a DC machine:
- Hence,
the correct answer is:
Correct Answer
✅ Option (a): Coils
✔️ Key One-Line Exam Statement
In a DC machine, the number of commutator segments is
equal to the number of armature coils.