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Ch – 26 Electric Field
Electric Field Model
• One or more charges
(source charges) alter the
space around them by
creating an electric field, E.
• A separate charge (test
charge or probe)
experiences a force F,
exerted by the field.
• F = qE
Electric Field of a Point Charge
The unit vector points outward from
the source charge
If q is negative the vector is reversed
and points inward, toward the source
charge
Electric Field Simulation
Electric field of a dipole
• Two equal and
opposite charges
small distance apart
• Zero net charge but it
causes an E field
• Dipole moment:
p = qs, pointing from
negative to positive
Electric Field of a Dipole
E Field for an Infinite line of Charge
Picturing the Electric Field
Electric Field of a Dipole
E Field for an Infinite line of Charge
Electric Field of a Ring of Charge
(Ering)z = [1/(4πε0)] [zQ/(z2+R2)3/2]
Electric Field of Charged Disk
Limit as R  ∞
Note that this value of E does not depend on the
distance from the charged plane (z), only on the
surface charge density
Electric field strength of an infinitely
charged plane is independent of
distance from the charge
Parallel Plate Capacitor
A parallel plate capacitor provides a uniform
electric field.
Motion of a charged particle in a
uniform electric field
• a = F/m = qE/m =
constant
• direction of a parallel
to E
• charged particle will
accelerate/decelerate
in the direction of E
• projectile motion, if v0
is not parallel to E
Motion in a Nonuniform Field
• circular motion of a
charged particle
around a point
charge, charged
sphere or wire
|q|E = mv2/r
Simulation lab
Superposition problem
Earth’s internal structure
Figure 1.13
Plate tectonics: the
new paradigm
Plate boundaries
• Types of plate boundaries
• Divergent plate boundaries (constructive
margins)
• Two plates move apart
• Mantle material upwells to create new
seafloor
• Ocean ridges and seafloor spreading
• Oceanic ridges develop along welldeveloped boundaries
• Along ridges, seafloor spreading
creates new seafloor
Figure 15.10a
Figure 15.12
Plate tectonics: the
new paradigm
Plate boundaries
• Types of plate boundaries
• Convergent plate boundaries (destructive
margins)
• Oceanic-continental convergence
• Denser oceanic slab sinks into the
asthenosphere
• Pockets of magma develop and rise
• Continental volcanic arcs form
• Examples include the Andes,
Cascades, and the Sierra Nevadan
system
Figure 15.14a
Plate tectonics: the
new paradigm
Plate boundaries
• Types of plate boundaries
• Convergent plate boundaries (destructive
margins)
• Oceanic-oceanic convergence
• Two oceanic slabs converge and one
descends beneath the other
• Often forms volcanoes on the ocean
floor
• Volcanic island arcs forms as
volcanoes emerge from the sea
• Examples include the Aleutian,
Mariana, and Tonga islands
Figure 15.14b
Plate tectonics: the
new paradigm
Plate boundaries
• Types of plate boundaries
• Convergent plate boundaries (destructive
margins)
• Continental-continental convergence
• When subducting plates contain
continental material, two continents
collide
• Can produce new mountain ranges
such as the Himalayas
Figure 15.14c
Plate tectonics: the
new paradigm
Plate boundaries
• Types of plate boundaries
• Transform fault boundaries
• Plates slide past one another
• No new crust is created or destroyed
• Transform faults
• Most join two segments of a midocean ridge
• Aid the movement of oceanic crustal
material
Figure 15.16