Download Electromagnetism - Sterling Public Schools

Electromagnetism
It’s attractive!
(or repulsive)
Electromagnetism rules
• Magnetic fields exist in the
region near a conductor when
the circuit is closed.
• The direction of the field is
dependent on the direction of
the current in the conductor.
The intensity or strength of an
electric or magnetic field can be
determined by the lines representing
it. The field intensity is proportional
to the number of lines of force per
unit area normal to the field. High
intensity is represented by lines
drawn close together, low intensity
is represented by lines more widely
separated.
Electric field intensity: E = F/q
in Newtons/Coulomb
Magnetic Flux density: B = Φ/A
in Webers per meter squared
Ampere’s Rule for a Straight
Conductor:
Grasp the conductor in the left
hand with the thumb extended in the
direction of the electron current.
The fingers then will circle the
conductor in the direction of the
magnetic flux.
Ampere’s Rule for a Solenoid:
Grasp the coil in the left hand
with the fingers circling the coil in
the direction of the electron
current. The extended thumb will
point in the direction of the North
pole of the core.
Electromagnetic
Induction
• An electric generator converts
mechanical energy to electrical
energy.
• An electric motor converts
electrical energy to mechanical
energy.
Generator Rule
Left Hand
Extend thumb, forefinger, and the middle finger of the
left hand at right angles to each other. Let the
forefinger point in the direction of the B flux from
North to South and the thumb in the direction the
conductor is moving. The middle finger points in the
direction of the induced electron current.
Motor Rule
Right Hand
Extend the thumb, forefinger, and middle finger of the
right hand at right angles to each other. Let the
forefinger point in the direction of the B flux and the
middle finger in the direction of the electric current. The
thumb points in the direction of the motion of the
conductor.