Grade 12 IEB Physical Science (Physics) Electrodynamics (Section F) Summary & notes

Electrodynamics:
Electromagnetism: Conventional direction of magnetic eld:




Current in electrodynamics = conventional current (ie. + to -) (NOT electron current)




• Magnetic e ect of electric current: A magnetic eld exists around a current-carrying conductor

• Right hand rule: Thumb points in direction of conventional current (+ to -) and ngers point in

direction of magnetic eld (lines)
+




Dot: Current Cross: Current
perpendicularly perpendicularly
out of page into page



• Magnetic eld around circular wire:

, • To determine magnetic poles of solenoid: Right Hand Solenoid Rule

Solenoid produces magnetic eld lines similar to bar magnet:




• Strength of electromagnetism:

- More turns on solenoid

- Bigger current

- Easily magnetised core (soft iron)



By placing current-carrying wire in magnetic eld, there is interaction between 2 magnetic elds




(current into page) (Current out of page)




Motor e ect: Current-carrying conductor experiences a force in a magnetic eld


F = I:l:Bsinµ
• F : Force (Newton, N)
• I : Current (Ampere, A)
• L : Length of conductor in B eld (metres, m)
• B : Magnetic ux density ( eld strength)
• µ : Angle between current and magnetic eld lines




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