Motors

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# Motors - PowerPoint PPT Presentation

Motors. A current in a wire is subject to a magnetic force. Magnetic field out of loop Perpendicular to plane A loop of wire will have a force on each segment. Simplify as rectangle Force directed inward. Wire Loop. I. F M. F M. F M. B.

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## PowerPoint Slideshow about 'Motors' - diamond

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Presentation Transcript

### Motors

A current in a wire is subject to a magnetic force.

Magnetic field out of loop

Perpendicular to plane

A loop of wire will have a force on each segment.

Simplify as rectangle

Force directed inward

Wire Loop

I

FM

FM

FM

B

Constant force on wires parallel to axis

Varying lever arm depending on rotational position.

Net torque to restore loop to 0° angle.

Magnetic Torque

l

FM

w

FM

B

The loop would come to stable equilibrium from the torque.

Flip current every half turn.

Inertia pushes it past equilibrium

Flipped torque from opposite current

The field provides torque for the next half-turn.

Repeat current flip

Current Flips

FM2

l

FM1

w

B

The coil is called the armature.

Usually many loops

Fixed permanent magnet provides the field.

DC Motor

Britannica.com

A brushless motor puts the magnet on the rotating shaft.

Switches control current flips to the electromagnets.

Easier to cool

Longer lasting

Brushless Motor
A galvanometer measures current with the motor principle.

Current in a coil is deflected by a field.

A spring provides a counter restoring force.

Greater deflection comes from greater current.

Galvanometer

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