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Electricity & Magnetism
A quick review of what we’ve learned…
through videos!
Relating Electricity & Magnetism
 Watch this video.
Create some hypotheses to explain what you saw.
Relating Electricity & Magnetism
1. Under what conditions did the wire jump?
2. Are stationary electric charges affected by magnetic
fields?
3. What about moving electric charges?
Relating Electricity & Magnetism
 How can we explain this behavior thinking about
magnetic fields?
 Pg. 563, Figure 2
Motor Principle
A current-carrying conductor crossing
an external magnetic field, experiences a force
perpendicular to the magnetic field and the
direction of the current.
Motor Principle
Right Hand Rule #3
- Thumb in direction of conventional current
- Fingers in direction of magnetic field
- Palm facing direction of force
Practice
 Determine the direction of the force on the conductor:
Motor
Parts of a Motor
Cell – Provides current
Field magnet – Provides
external magnetic field
Coil - Part of the motor that
rotates (armature)
Commutator – “Split ring” that
rotates with the coil
Brushes – Connects
commutator and cell
Motor Principle
 For a motor to turn
continuously, the
current must change
direction in the loop.
In a DC or directcurrent motor, this is
accomplished with
brushes & the splitring commutator
Parts of a Motor
 Name the parts of the motor that are labelled in the
diagrams below!
Motor Principle
Motor Principle
Motor
Motor Principle
Motor
Motor
Motor
Homework
Pg. 566 #1, 2
Pg. 571 #1, 2