Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A coil of turns, each of area , carries in a field of . Its turning effect is , where is the angle between the plane of the coil and the field. Find when the coil lies along the field (), when , and when .
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 .
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. .
Step 2. At . .
Step 3. At . .
Step 4. At . : the forces pull straight outward.
Answer: , and .
Check. The turning effect is largest along the field and falls to zero at right angles, where the split ring reverses the current.
Log in to join the discussion.
Loading…