Magnetism

• the fundamental nature of magnetism is the interaction of moving charges
• a moving charge produces a magnetic field in the space around it
• a second current responds to the magnetic field produced by a moving charge
• permanent magnets


  found to exert forces on each other
• a distribution of electric charges create an electric field in the surrounding space
• the electric force exerts a force on any other charge that is present in the field
• a moving charge creates a magnetic field in the surrounding space
• the magnetic field exerts a force on any other moving charges or current present in the field
• magnetic interactions are fundamentally interactions between moving charged particles
• right hand rule for the direction of magnetic force on a positive charge
• the magnetic moment of a loop depends only on the current and the area
• a current loop with area and current in a uniform magnetic field experiences no net magnetic force but experiences a magnetic torque
• solenoid


  a helical winding wire
• in a motor, a magnetic torque acts on a current-carrying conductor and electric energy is converted into mechanical energy
• in a dc motor, a magnetic field exerts a torque on a current in the rotor
• motion of the rotor through the magnetic field causes an induced emf called back emf
• hall effect


  is a potential difference perpendicular to the direction of the current in a conductor
• hall potential


  determined the requirement that the associated electric field must just balance the magnetic force on a moving charge