Superposition Principle

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Superposition Principle
The net electric field at a location in space is
the vector sum of the individual electric fields
contributed by all charged particles located
elsewhere. The electric field contributed by a
charged particle is unaffected by the presence of
other charged particles.
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Dipole
A dipole is a set of equal magnitude, oppositely
charged particles.
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Efield due to a dipole - on axis
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Efield due to a dipole - on perp. bisector
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Efield due to a dipole on axis - derivation
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Efield due to a dipole on axis -far field
approximation
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Poll
A chloride ion (Cl-) is placed at location C.
What is the direction of the force on the
chloride ion?
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Efield due to a dipole on the perpendicular
bisector - derivation
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Efield due to a dipole on the perp. bisector -
far field approximation
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Poll
What is the direction of the electric field at
location C, due to the dipole?
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Poll
An alpha particle (He2) is placed at location B.
What is the direction of the force on the alpha
particle?
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Poll
A proton is placed at location D. What is the
direction of the net electric force on the proton?
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Efield at an arbitrary point
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Dipole Efield
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Dipole Moment
The dipole moment vector points parallel to the
efield on axis outside the dipole.
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Poll
The dipole moment vector points in the direction

• from -q to q
• from q to -q

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Poll
Along the axis of the dipole, at points outside
the dipole, the electric field points

• in the direction of the dipole moment
• opposite the direction of the dipole moment

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Poll
Along the perpendicular bisector of a dipole, the
electric field points

• in the direction of the dipole moment
• opposite the direction of the dipole moment

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Poll
What is the magnitude of the net electric field
at point D?
1. 2. 3. 4.
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Poll
s 2e-10 m and d 3e-6 m. What is the magnitude
of the electric field at location A?
1. 2.
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Summary