Transcript Magnetic Fields Produced by a Conductors

Magnetic Fields Produced by Conductors
13.3 and 13.4: The Right Hand Rule and Magnetic Fields of Solenoids
And how to switch on and off the strangely attractiveness
Effects of Domain Theory
• Magnetic Induction
• Demagnetization
• Reverse Magnetization
• Breaking a Bar Magnet
• Magnetic Saturation
• Induced Magnetism by Earth
• Keepers for Bar Magnets
Oersted’s Discovery
In 1819, the Danish physicist
Hans Christian Oersted
(1777-1851) discovered the
connection between
electricity and magnetism by
accident while lecturing at the
University of Copenhagen.
He noticed that a compass
needle placed closely to a
current carrying wire would
take up a position nearly
perpendicular to the
direction of the current.
Principle of Electromagnetism
Whenever an electric current
moves through a conductor, a
magnetic field is created in the
region around the conductor.
Magnetic Field of a Straight Conductor

The magnetic field lines for a straight conductor are
concentric circles around the conductor.
The RightHand Rule
• If a straight conductor is
held in the right hand with
the right thumb pointing in
the direction of the electric
current, the curled fingers
will point in the direction of
the magnetic field lines.
Parallel Wires
How is the scrap metal held up by the
crane?
Electromagnets


A device that exerts a magnetic force using electricity.
The magnetic field around a straight conductor can be
intensified by bending the wire into a loop.
Coil or Solenoid

The magnetic field can be further intensified by combining
the effects of a large number of loops would close
together to form a coil, or solenoid.
The RightHand Rule
• If a coil is grasped in the
right hand with the curled
fingers representing the
direction of electric current,
the thumb points in the
direction of the magnetic
field inside the coil.
Parallel Coils
Factors Affecting the
Magnetic Field of a Coil
Current in the
Coil
Number of
Loops
• The more current, • The more loops,
the greater the
the stronger the
concentration of
magnetic field
magnetic field lines
since the magnetic
in the core.
field is the sum of
the field of each
loop.
Type of Core
Material
• The core of a coil
can greatly affect
the coil’s magnetic
field strength.
• A core of iron will
increase the
strength compared
to that of air.
Type of Core Material


The core material becomes an induced magnet, as its
atomic dipoles align with the magnetic field of the coil.
The core itself becomes an induced magnet.
The factor by which a core material increases the
magnetic field strength is called the material’s relative
magnetic permeability (K).
Ferromagnetism
• Materials that become strong induced magnets when
placed in a coil.
• Iron, nickel, cobalt, and their alloys.
Paramagnetism
• Materials that magnetize slightly when placed in a coil and
increase the field strength by a barely measurable amount.
• Oxygen and aluminum.
Diamagnetism
• Materials that cause a very slight decrease in the magnetic
field of a coil.
• Copper, silver, and water.
Applications of Electromagnetism