Difference Between Split Ring and Commutator 

If you’ve ever revised electric motors and found yourself muttering “Wait… isn’t a split ring just a commutator?” — you’re not alone. Textbooks, notes, and even some websites explain this in slightly different ways, which makes it feel more confusing than it really is.

Let’s clear it up properly, in a way that sticks.

• Quick answer in one breath: A split ring is the physical copper ring cut into two halves that sits on the motor shaft and reverses the current in a simple DC motor. A commutator is the whole current-reversing switch assembly (the split ring plus its brushes, or the multi-segment version in bigger DC machines) that keeps torque in the same direction. 

1. First, what exactly is a split ring?

Imagine a copper ring wrapped around a motor shaft. Now slice that ring into two separate semicircles, and insulate them from each other. Each half connects to one end of the armature coil. As the coil spins in a magnetic field, each half of the ring takes turns connecting to the positive and negative terminals via brushes, flipping the current direction every half turn.

That sliced copper ring is the split ring. It’s most commonly seen in simple school-level DC motors, where the goal is to keep the coil turning in one direction by reversing current at just the right moments. 

• Key things about a split ring:
  • Made of two (or a few) copper segments, insulated from each other.
  • Mounted on the rotor/armature shaft.
  • Each segment connects to one end of the coil (armature winding).
  • Works together with brushes that press on the ring surface.
  • Its job: reverse the current direction in the coil every half turn, so the torque direction stays the same and the motor keeps spinning. 

2. So then… what is a commutator?

“Commutator” is more of a concept + assembly than a single piece of copper.

In DC motors and generators, a commutator is the rotary switch that:

• connects the rotating windings (armature) to the outside circuit, and
• periodically reverses the current direction in those windings so the machine produces continuous torque  or direct current (generator). 

In a small DC motor, the commutator is often just a simple split ring plus the brushes. In a larger machine, the commutator is built as a cylinder of many copper segments, each connected to different coils on the armature. Brushes slide over these segments as the rotor spins, performing continuous “electrical re-wiring” in real time. 

• Key things about a commutator:
  • It’s a mechanical switching device, not just a ring.
  • Used mainly in DC motors and DC generators (dynamos), and in universal motors that can run on AC or DC. 
  • Built from multiple copper segments arranged around the rotor.
  • Works with stationary brushes to route current into and out of the rotating armature.
  • Its job: reverse current at the right times so:
    • in motors → torque keeps pushing in one direction;
    • in generators → the output becomes (essentially) DC instead of AC.

3. The subtle relationship: split ring vs commutator

Here’s the bit most students (and some sites) gloss over:

In simple school-level DC motors, the split ring and the commutator are closely related ideas. Many exam boards and resources even call it a “split-ring commutator”, treating the term as a synonym. 

But if we zoom out to real-world machine design:

• A split ring is:
  • a specific type of commutator construction (two copper halves),
  • used in simple DC motors to reverse current.
• A commutator is:
  • the entire switching system (segments + brushes),
  • can have many segments, not just two,
  • and exists in most brushed DC machines.

In many textbooks, you can think of it this way:

Split ring = the “hardware piece”; Commutator = the “role + assembly” that uses that hardware. 

• Exam-safe way to phrase the difference:
  • Split ring: A ring cut into two or more insulated sections, used (with brushes) in simple DC motors to reverse current direction in the coil every half-turn.
  • Commutator: The rotating switching device (made of one or more copper segments plus brushes) used mainly in DC machines to reverse current direction or to convert AC in the armature into DC at the terminals.

4. Comparison table: split ring vs commutator

Here’s a side-by-side view so your brain can park the concepts neatly:

5. How the split ring acts as a commutator in a DC motor

Let’s walk through one mental animation.

Picture a simple DC motor:

1. There’s a rectangular coil of wire in a magnetic field.
2. The coil’s two ends connect to the two halves of the split ring.
3. Two carbon brushes press lightly on the split ring halves and are connected to the battery.

As the coil turns:

• For the first half-turn, one side of the coil is connected to +ve and the other to −ve.
• Just as the coil passes the vertical position (where torque would otherwise reverse), the split ring halves swap which brush they touch.
• That instantly reverses the direction of current in the coil — but the magnetic field is the same — so the torque direction stays the same and the motor keeps spinning in one direction. 

In other words, the split ring is acting as the commutator: it “commutes” (switches) the current at just the right time.

• Step-by-step operation (revision friendly):
  • Coil carries current → experiences a force in the magnetic field → starts to rotate.
  • Approaching vertical, torque would normally drop and change direction.
  • At this moment, the split ring’s halves swap brushes, flipping the connections to the battery.
  • Current in the coil reverses → force direction on each side of the coil also reverses.
  • Result: torque keeps pushing in the same rotational direction, so the motor doesn’t get “stuck” rocking back and forth.

6. Where students (and interviewees) get tripped up

A lot of confusion comes from three similar-sounding components:

• Slip ring
• Split ring
• Commutator

Slip rings often appear in AC machines and in special DC cases like homopolar motors, where they provide continuous electrical contact without reversing current. 

Split rings, by contrast, are deliberately cut so they can reverse current.

• Common misconceptions clarified:
  • “Split ring and commutator are completely different things”
    • Not quite. A split ring is a type of commutator used in simple DC motors. In that context, “split-ring commutator” is perfectly correct. 
  • “Slip ring and split ring are basically the same”
    • No. Slip rings give a continuous connection (no current reversal), used in AC generators and some motors. Split rings are cut to reverse current in DC motors. 
  • “A commutator always has only two segments”
    • In simple diagrams maybe, but real DC machines often have dozens or even hundreds of segments for smoother torque and voltage. 

7. Memory hacks & analogies

Let’s give your brain a couple of hooks so you never mix these up in an exam or viva.

Think of the whole motor like a DJ setup:

• The coil is the music track.
• The commutator is the DJ’s mixer that flips and routes signals.
• The split ring is one specific style of mixer — a simple two-channel crossfader that flips left and right.
• The brushes are the DJ’s hands constantly touching the controls, making the switch happen.

• Quick mnemonics:
  • “Split ring: split to flip.”
    • If it’s split, its job is to flip the current direction.
  • “Commutator: commits to direction.”
    • It keeps the torque or output current going one way, even though the coil current is being reversed inside.
  • “Slip = smooth.”
    • Slip ring = smooth, continuous connection, mainly in AC machines (no intentional flip).

8. Final recap: how to answer in one solid, exam-ready line

If you’re writing a short answer, here’s a clean way to put it:

A split ring is a copper ring cut into insulated halves and used in simple DC motors to reverse the current in the coil every half-turn. A commutator is the rotating switching device (segments + brushes) used mainly in DC machines to reverse or route current so that torque or output current remains unidirectional; the split ring is one simple form of commutator.

That gives you:

• the hardware idea (ring vs assembly),
• the function (current reversal), and
• the context (simple DC motor vs general DC machines).