Electromagnetism

Electromagnetism

1. A current-carrying conductor/wire produces a magnetic field around it.

   • Direction of magnetic field depends on direction of current
     • Right Hand grip rule
   • When wire is a coil, right hand grip rule to determine direction of pole
     • strength of magnetic field determined by:
       • Increasing current through solenoid
       • Increasing number of coils in same length
       • placing soft iron core in solenoid (magnetic field will flow thru it)

2. Force on current-carrying conductor due to magnetic fields

   • When a current carrying conductor in placed in a magnetic field, it will experience a force (Fleming's left hand rule)
     • if magnetic field lines point in same direction, magnetic force is stronger. If facing different direction, they cancel out so weaker force.
       • Difference in force strength results in force towards the weaker field
         • in this example, wire will go downwards
     • When reverse EITHER direction of magnetic field or direction of current, direction of force reverses.
       • If BOTH reverse, direction of force remains the same

3. D.C. Motor

   • using the motor effect n changing direction of current, result in turning effect
     • Features
       • Split-Ring commutator
         • Split in ring allows for direction of current to be reversed every half-rotation
       • Carbon brushes
         • conduct electricity to wire, and is also a lubricant that allow commutator to turn with minimal friction
     • How it works
       • when coil is in vertical position, current is cut off as split ring not in contact with carbon brush
         • momentum carries it onto horizontal position
         • at horizontal position, commutator in contact with brush, and will result in motor effect until next vertical position
     • How turning effect can be increased
       • Increase number of turns in wire coil
         • Increase number of current through the coil
           • Increase strength of magnetic field strength of magnets
             • adding soft iron core

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