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 (E ring ) z = [1/(4πε 0 )] [zQ/(z 2 +R 2 ) 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 v 0 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 = mv 2 /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 well- developed 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 mid- ocean ridge Aid the movement of oceanic crustal material

Figure 15.16