Why does the DC motor diagram omit field direction at points A and D?

[ellieee]

Homework Statement

in every d.c motor, is it always the case that the current at coil "a" is flowing into the plane and current at coil "d" is flowing out of the plane?

Relevant Equations

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^because in my textbook, the set up doesn't even show the direction of dot/cross at points A/D, so we won't know the direction of current. then how are we supposed to use fleming's left hand rule to determine the direction of force?

 

[DaveE]

I don't understand your question. The current polarity is clearly shown with the battery as well as arrows on the rotor winding. The magnetic field polarity is also shown with N-S labels. The current flows in the plane of the rotor, which is rotating. Then once per cycle, the current switches polarity.

 

[ellieee]

I don't understand your question. The current polarity is clearly shown with the battery as well as arrows on the rotor winding. The magnetic field polarity is also shown with N-S labels. The current flows in the plane of the rotor, which is rotating. Then once per cycle, the current switches polarity.

oh I see it now thank you !

 

[Tom.G]

The 'Dot', 'Cross' symbols are taken from how a target arrow (as used in archery) looks when viewed from the end. The 'Dot' is the tip of the arrow coming towards you, and the 'Cross' is the fletching (feathers) on the other end of the arrow going away from you.

Note that this is Conventional Current flow, '+' to '-', Not Electron flow.

Hope this helps!

Cheers,
Tom