10/24/2013
Induction
CHARGING BY
INDUCTION (BOTH
TEMPORARY AND
PERMENANT)
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Induction
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The movement of electrons within a
substance caused by a nearby charged
object, without direct contact between the
substance and the object.
Example 
When a charged object is near a neutral
object, the electric field of the charged
object has an effect on the neutral object.
The charged object induces electrons in the
neutral object to move.
Induction happens WITHOUT any touching
of the neutral/charged object (no contact!)
Temporary Charge by Induction
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
When a charged object is brought close, but DOES
NOT TOUCH a neutral object, the electrons are
induced to move within the neutral object.
This neutral object now has a “temporary” charge
that is opposite to the charged object.
The balloon is NEGATIVELY charged
and the wall is NEUTRAL.
But – when you bring the balloon close to the
wall – the electrons move away because
of repulsion (a POSITIVE charge is
INDUCED).
Temporary Charge by Induction
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
The sphere is neutral to start.
Then a negatively charged rod is brought close to it
(but it does NOT touch).
The sphere has a temporary positive charge (the induced
charge is always opposite).
**No electrons are transferred here**
Temporary Charge by Induction
After the rod is taken away the sphere
will go BACK to being neutral and the
electrons will be redistributed. This is
why it is said to be TEMPORARY!
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10/24/2013
Permanent Charge by Induction
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In order to make a PERMANENT charge through
induction – a charged object is brought close to a
neutral object (without touching).
Review – What is Grounding?
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While the charged object is held close, the neutral
object is grounded  this allows the charge to
remain permanent!

This can be done with positive or negative charges!
Neutral object
Permanent Charge by Induction
Object is grounded
Negative rod brought close
-causing a temporary positive charge -either with a conductive wire
or a finger

Negative rod is removed after
grounding has occurred
The neutral object is now permanently
with a positive charge!
Grounding is when an electric discharge happens by
connecting a charged object to the Earth
(through a conducting material).
If a build up of extra electrons is on an object
(NEGATIVE charge), the electrons will flow: from
the object TO the Earth.
If there is a lack of electrons on an object
(POSITIVE charge) – the electrons will flow: from
the Earth TO the object.
The induced charge is always opposite to that of the
charged object producing the charge.
A negative rod will produce a positive induced
charge.
A positive rod will produce a negative induced
charge.
*NOTE* - the finger/grounding wire needs to be removed before
taking away the charged rod!
Positive Permanent Charge by Induction
We already saw an example similar
to this on a previous slide!
Negative Permanent Charge by Induction
Notice the movement of electrons!
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