Electric Fields

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A region in space in which an electrostatic force
acts on a charge
Exists around every charged object
Mapped by drawing field lines (indicate the
direction of the electrostatic force an a + test
charge placed in a field.)
It is a vector quantity
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Magnitude is equal to the force exerted per unit
charge at that point in the electric field.
What does this translate to mathematically?
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Where:
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E is the magnitude of the electric field
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F is the magnitude of the force
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q is the magnitude of the charge
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F is measured in Newtons
q is measured in Coulomb’s
What will E be measured in then?
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F/q = Newtons/Coulomb’s = E
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What is the magnitude of the electrostatic force
experienced by one elementary charge at a
point in the electric field where the electric field
intensity is 3.0 x 103 N/C?
B
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A
Point A is 1 meter from sphere, so E = 9 N/C
Point B is 3 meters from sphere, so E = ?
Based on your answer from the previous slide,
where is E stronger?
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E α 1/d2
E
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E=0
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B
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What is E for each point?
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Do Now: Fill out the scantron for the
Winter Break Assignment
HW: Quiz tomorrow on Coulomb’s
Law and Electric Fields
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v
Curved path due to electric field on charged particle
Older TV’s and inkjet printers use this technology
Existing Electric Field
F
+q
d
Fe
If we push a charge opposite the field direction, work is done
WE = F&middot;d
Since W = ΔPE, the charge has more potential energy at the
final location.
V = W/q
V = F&middot;d/q
V = Ed
W = F&middot;d for a constant Force (constant field)
F/q = E
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