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Explanation of the Electric Motor Demonstrated in Class

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Rotor or armature(the rotating piece of the motor)

Explanation of the Electric Motor Demonstrated in Class

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I IBext Bext

Coils (or bar magnets) are used to create the external magnetic field

Bcoil

Follow the wires and find this direction of current at this instant

Which induces this B-field

Explanation of the Electric Motor Demonstrated in Class

To align the B-fields, a CW torque is created. In this position, the torque is maximum

Rotor or armature(the rotating piece of the motor)

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I IBext Bext

The rotor rotatesBcoil

Explanation of the Electric Motor Demonstrated in Class

In this position, the angle between Bcoil and Bext has decreased, so the torque has decreased

τ=0

Bcoil

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The rotor continues to rotate

In this position, the B-fields are aligned and the torque is zero

Explanation of the Electric Motor Demonstrated in Class

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B coil

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Momentum carries the rotor further around

Follow the wires in this position and find that the current in the coils has changed direction

Inducing a B-field in this direction

And so the torque continues to be clockwise.

Explanation of the Electric Motor Demonstrated in Class

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Bcoil

The rotor rotates to this position, which is 180º from where it started.Since the current and Bcoil have switched directions, it is essentially the same configuration as it was at the start.

Explanation of the Electric Motor Demonstrated in Class

And so, the process repeats…