Download Electric Fields PPT

Electric
Field
Property of space around a
charged object that causes forces
on other charged objects
Measuring the Field Intensity
of a Charged Object
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To determine the intensity of a
field, use a test charge q’ at any
given point from the object being
tested. The test charge is a small
positive particle.
According to Coulombs Law the
closer the test charge the stronger
the force
The field can be determined by the effects on the test
charge in different locations
Field Intensity = E = is proportional to the
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force on the test charge
and inversely
proportional to the
charge itself. This ratio
is independent of the
test charge.
qq '
k
Fkq
(on q') r 2
E  E 2
r q' q '
The direction is the direction of a positive (+)
charge toward a negative (-) charge
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Test Charge
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Field Line
s
Field Lines Represent the Intensity and Direction of the
Electric Field
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Unlike
Like Charges
Charges
Direction of
Electric Field
The electric field direction is always directed away from positive source
charges and towards negative source charges.
Electric Field
Intensity
The greater the number of electric field lines. The greater the field intensity.
The density of electric field lines around these three objects reveals that the
quantity of charge on C is greater than that on B which is greater than that on A.
1. The closer together the lines of force, the stronger the
electric field.
2. The directions of the electric field is tangent to the
lines of force.
3. The electric field lines start at positive charges and end
on negative charges.
4. The number of lines leaving or entering a charge is
proportional to the magnitude of the charge.
Conductors and Electric Field
Excess charge tends to accumulate
at sharp points, or locations of
greatest curvature, on charged
conductors. The places of highest
charge accumulation are where
the electric field from the
conductor is the largest
Electric field is zero everywhere
inside a charged conductor
Any excess charge on an
isolated conductor resides
entirely on the surface of the
conductor
The electric field at the outer
surface of a charged conductor is
perpendicular to the surface
Gauss’s Law for Electric Fields
The net number of electric field lines passing through
an imaginary surface is proportional to the amount of
net charge enclosed within that surface