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7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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Maria Carmela T. Garcia
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1st
semester 2013-2014
Why is it that when you walk on a carpeted floor andreach for a door knob, you sometimes get a littleshock?
Why do you sometimes get this same little shock whenyour arms bumps against your friend as you arewalking in the mall?
Why does your hair stand on end after removing your
cap on a cold day?
What causes lightning?
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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www.school-for-champions.com
safe4work.orgscienceblogs.com
Atoms primarily consist of
Positively charged protons
Neutral neutrons
Negatively chargedelectrons that orbit the
nucleus at high speeds.
www.universetoday.com
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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The charged particles electrons and protons have the same magnitudeof charge, which is
e = 1.6 10-19 C
www.universetoday.com
Some materials hold their electrons verytightly.
These materials are called insulators.
Other materials have some loosely heldelectrons, which move through them veryeasily.
These are called conductors.
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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Positively
Charged
Uncharged/
Neutral
Negatively
Charged
More protons than
electrons
Equal number of
protons and electrons
More electrons than
protons
7198.185.178.104
Unit of Charge: Coulomb, C
Static electricity is the imbalance of positive andnegative charges.
Conservation of Charges
Charges are neither created nor destroyed.
Theytransferfrom one object to another.
Properties of Charges
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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Quantization of Charges
Electric charge (Q) always occurs as some
integral multiple of the fundamental
charge e
Properties of Charges
Like charges REPEL, unlike chargesATTRACT
Holzner, Stephen. 2006. Physics for Dummies. Wiley Publishing
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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Charged objects can also attractsomething that is neutral.
Holding it near a neutral object will makethe charges in that object realign.
corresponds to a
rearrangement of thebound electrons in the
material.
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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There are three ways to charge an object
By friction
By conduction
By induction
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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whs.wsd.wednet.edu
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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tutorvista.com
When the air is very dry, it becomes lessconductive
When the air is humid, the water in the air allowsthe electrons to move off you more quickly
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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http://scijinks.nasa.gov/lightning
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7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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www.frankswebspace.org.uk
Weve talked about how like charges attract, and
unlike charges repel
The presence of an electric charge produces a
force on all other charges present.
The electric force produces action-at-a-
distance; the charged objects can influence each
other without touching.
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7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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What is the repulsive force between twoelectrons that are 1m apart?
Electrically charged object generatean electric field in the space aroundit
This field exerts the pushes or pullsto other charged objects in the
surrounding area. The electric field is a vector field.
The electric field is
a vector field.
7/27/2019 09 Physics in Circuits and Gadgets (Part 1)
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f i e l d l i n e s n e v e r i n t e r s e c t !
f i e l d l i n e s n e v e r i n t e r s e c t ! f i e l d l i n e s n e v e r i n t e r s e c t !
f i e l d l i n e s n e v e r i n t e r s e c t !
http://2.bp.blogspot.com/-sEfvf1izXBo/TeZZNGTopmI/AAAAAAAAAKo/7s1k1eWpdg0/s1600/E_field.png
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Electric field is expressed in Newtons perCoulomb (N/C) and use the symbol E.
What is the magnitude of the electric fieldE at a field point 2.0 m from a point chargeq = 4.0 nC?
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