Transcript Electric Fields - Mansfield Public Schools

Electric Fields
The Electric Field
Electric Fields Lines
Field due to a Point Charge
Field due to an Electric Dipole
Field due to a Line of Charge
Field due to a Charged Disk
Point Charge in an Electric Field
Dipole in an Electric Field
pps by C Gliniewicz
When gravity was first discussed, we hardly used the term gravitational field, but
one can think about how a mass knows there is a gravitational force. One can say
that a “field” exists which explains a force at a distance. The same can be said or
the space around an electric charge. An electric field exists around the charge.
For the gravitational field
For the electric field
Unlike the gravitational field which always points toward the mass producing the
field, electric fields point away from a positive charge and electric fields point into
a negative charge.
Field lines never cross. When opposite charges attract, the field lines connect the
positive charge to the negative charge. When like charges are near each other, the
field line do not connect the charges together.
pps by C Gliniewicz
The electric field at any point is the vector sum of the electric fields due to all the
charges around the point in question.
An electric dipole consists of two equal and opposite charges at a constant
separation. The direction of the dipole points from the positive toward the
negative charge.
The dipole moment is denoted by the letter, p. The
distance between the charges is labeled, d.
The electric field due to the dipole along the axis of the dipole (the z axis)
A charge distribution consisting of a large number of closely spaced charges are
said to be continuous. Charge density can be defined along a line, on a surface or
throughout a volume.
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The electric field at some distance, r, from the line of charge is
If the line of charge forms a circle, one can determine the electric field along the
axis passing through the center of the circle of radius, R.
At some distance z>>R,
At some distance, z, along the axis of a disk with uniform charge on the surface, the
electric field is
The electric field at some distance from an infinite sheet of charge is
When the electric field is great enough to remove the electrons from the atoms in
the air, the electrons are set into motion and the atoms emit light, a spark. The is
called electrical breakdown.
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When an electrical dipole is placed in an electric field, the dipole experiences a
torque.
Potential energy in a dipole can be calculated by determining the integral of the
torque and angle.
pps by C Gliniewicz