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.
Magnetic field out of loop
Perpendicular to plane
A loop of wire will have a force on each segment.
Simplify as rectangle
Force directed inwardWire Loop
Constant force on wires parallel to axis
Varying lever arm depending on rotational position.
Net torque to restore loop to 0° angle.Magnetic 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 flipCurrent Flips
The coil is called the armature.
Usually many loops
Fixed permanent magnet provides the field.DC Motor
Switches control current flips to the electromagnets.
Easier to cool
Longer lastingBrushless Motor
Current in a coil is deflected by a field.
A spring provides a counter restoring force.
Greater deflection comes from greater current.Galvanometer