EasyPhysicsHigh School (9–10)Electricity & Magnetism › Magnetic Effects of CurrentConceptualBoard Exam
What is the job of the split ring (commutator) of a DC motor? …
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
- What is the job of the split ring (commutator) of a DC motor?
- What would happen with one complete ring instead?
- A motor turns times a second. How many times each second does its split ring reverse the current?
Need a reminder? The key ideaShow
In a motor, the two sides of a coil feel opposite forces, so the coil turns. The split ring (commutator) reverses the current every half turn, so it keeps turning one way. The largest turning effect is ; at an angle between the coil's plane and the field it is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) It reverses the current in the coil every half turn, so the forces keep turning the coil the same way.
Step 2. (b) With a complete ring, the current would not be reversed. After half a turn the forces would turn the coil back, and it would only rock to and fro.
Step 3. (c) reversals each second.
Answer: it keeps the coil turning one way; the coil would rock; times a second.
Check. Two reversals in each turn and turns each second give reversals each second.
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