1. ECE 201 Circuit Theory I1 Interaction of Magnetic Fields (Motor Action) Look at adjacent current-carrying conductors –Currents in opposite directions –Flux “bunching” between the conductors –Force of repulsion acts to separate the conductors

2. ECE 201 Circuit Theory I2 Interaction of Magnetic Fields (Motor Action) –Currents in the same direction –Flux in space between conductors in “opposite” directions –Force of attraction acts to pull the conductors together

3. ECE 201 Circuit Theory I3 Elementary Two-Pole Motor Rotor core with 2 insulated conductors in “slots” A stationary magnet – the “stator”

4. ECE 201 Circuit Theory I4 Current-Carrying Conductor in a Magnetic Field Current-carrying conductor perpendicular to the B-field

5. ECE 201 Circuit Theory I5 Magnitude of the force on the conductor in a Magnetic Field Magnitude of the mechanical force on the conductor is Where F = mechanical force (N) B = flux density in the stator field (T) = the effective length of the rotor conductor I = current in the rotor conductor (A)

6. ECE 201 Circuit Theory I6 Conductor “skewed” to the B-field by angle  = effective length of the rotor conductor (m) l effective

7. ECE 201 Circuit Theory I7 Single-Loop Rotor Coil Carrying a Current Situated in a Two-Pole Field

8. ECE 201 Circuit Theory I8 Torque produced by the 2-conductor couple

9. ECE 201 Circuit Theory I9 Elementary Two-Pole Generator

10. ECE 201 Circuit Theory I10 Voltage induced in the coil, e Flux through the coil window is sinusoidal Φ = Φ max sin(ωt) Voltage induced in coil,e e = N(dΦ/dt) e = NωΦ max cos(ωt) E max = ωNΦ max E max = 2πfNΦ max E rms = 4.44fNΦ max

11. ECE 201 Circuit Theory I11 Directions of induced voltage and current Develop CCW counter- torque “Bunching” must occur at the top of coil side B and the bottom of coil side A Coil current is CCW as viewed from south pole