1. Principles of Electromechanics Electricity  Motion Electricity  Motion: Motor Motion  Electricity: Generator  Magnetic Field & Faraday’s Law

2. Magnetic Field 1.Generation of magnetic field Permanent Magnet: Electric Current: using right hand rule to determine the field direction Straight current Current coil N S

3. Current  Motion: Current in magnetic field Magnetic field will exert a force on a current Magnetic field will exert a force on a moving charge × × × I F -q V F r

4. Circular Motion: Plane  B × × × -q V F r Circular path: V || =0 Helical path: V ||  0

5. Charges in B field: Applications Mass Spectrometer: Cyclotron (accelerator)

6. Example: Rail Gun Acceleration: 5  10 6 g Final speed: 1 km/s Duration: 1 ms

7. Motion  Current: Generating Electricity (Faraday’s law) 1. A current appears only if there is relative motion. 2.Fast motion produces a greater current. 3. Clockwise/counter clockwise current with north pole move in/out. Opposite with south pole. Induced current in secondary coil, if there is change of current in the primary coil: switch or ac current Transformer

8. Faraday’s Law of Induction Magnetic flux through area A Amount of magnetic field passes through an area A Faraday’s Law of Induction: An emf is induced in a loop when the magnetic flux that pass through the loop is changing. The the loop is conducting, then a current will flow. For uniform B:(Weber, or Wb, or T m 2 For a loop with N turns: Change B (change current)Change AChange angle between them

9. Current loop in magnetic field: Motors BB  F F L  w 

10. Torque on a Current Loop: Motors B  F F B  F F B  F F   n n n

11. Torque on a Current Loop: Continuous B  F F   n B  F F n B  F F B  FF B  F F n