Transcript Electric charges - Churchill High School

Electron has a
_________ charge
______ has a no
charge
Proton has a
________ charge
But what is a charge?

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Electric charge, like
mass, is a _____________
___________ of matter.
Inside atoms found in
matter, ____________
between positive and
negative charges holds
the atoms together.
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Virtually ______________around
you has electric charge
because atoms are made of
electrons and protons (and
neutrons).
But.... ordinary matter has
____________________________,
most matter acts as if there is
no electric charge at all.
_______
_______
_______
_______
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Greater affinity for e- : stick to electrons
more and _______________________becoming
negative
Less affinity for e- : don’t hold electrons as
tight and are more ________________________
and become positive
Charging by Friction
 A _________does not have much affinity for
electrons.
 Becomes ____________
 PVC becomes ____________
(Hold electrons tightly)
Most likely to gain electrons and
become negative
(Hold electrons loosely)
Most likely to lose electrons and
become positive)
PVC
Rubber
Cotton
Paper
Silk
Fur
Wool
Nylon
Hair
Acetate
Glass
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Material through which ______________________

Examples (gold, silver, copper, and aluminum)
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The general rule is that good thermo
conductors are ___________________________
conductors
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Metals ____________________________ in
electron clouds
electrons are _____________________ around
making them better conductors.
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Material through which _________________
freely move
Examples: rubber, paper, plastic, air
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______________________________
by producing a path to the
ground
Electrons move _______________
charged objects ____________
until the object is neutral
Electrons move ________________
______________________ charged
objects
The earth both ______________
__________________ electrons
while remaining overall neutral
Grounding
wand for Van
De Graaff
generator
Section 2: Charging Objects
Three Ways of putting a charge on an
object
1.
2.
3.
1. Charging by Friction
 Charging by rubbing objects that have
different affinities for electrons together
Induction
(______________________
__________________)
1.
2.
Bring a charged object (rod) _________ a
neutral one (ball) without contact
The electrons in the ball will be
____________ leaving a positive side
- +- - + +
- -+- + +
+ + +
---
3.
The (now) _________________ball will
be attracted to the negative rod
Induction
(charging without
contact)



Induction is only a ____________ change
without contact therefore electrons are not
transferred
The charge induced is _______________
Take away the rod and a _______________
will return
- +- -- +- -+-- ++ +
- - -- -
+
+
+
-
Conduction
(__________________
__________________)


Conduction is a more permanent change
_______________; electrons are
________________ and then isolated.
Charge conducted is the ______________
+ +
- + +
- + +
- -

+- - -+-- -+-- -
After conduction the ball and rod _________
each other
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The unit of charge is the ____________ (C). The
name was chosen in honor of
Charles Augustin de Coulomb (1736-1806), the
French physicist who performed the first
accurate measurements of the force between
charges.

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Electric forces are
incredibly strong.
A millimeter cube of
carbon the size of a
pencil point contains
about _________________
of positive and negative
charge.
3 factors affecting the magnitude of the force
between two charged objects:
1.
________________ on the objects
2.
_________________ between objects
3.
_______________separating objects
When using this equation:

A positive force (F) signifies ________________
◦ Both charges (Qs) must be positive or both negative
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A negative force (F) signifies _______________
◦ One charge (Q1 or Q2) must be positive and the
other negative
el

Coulomb’s Law is similar to _________________________________
Similarities:
◦ They both are used to calculate a ____________________
◦ Both forces have an _________________relationship to distance
◦ They are both __________________________
Differences:
◦ Force of gravity is always __________________
◦ Electrostatic force _________________attractive or repulsive
◦ Gravities constant is very small since gravity is a ____________
force
◦ Fg relates force created by a _________________, Fel relates
force created by _______________
el
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Both electric and gravitational forces are field
forces because objects ______________________
to be subjected to the force.
Field forces are sometimes called “forces at a
________________.”
Magnetic forces work similarly.
Electrical Fields
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Electrical Field (E): an ______________________
__________________ around a charged object.
Variable E
Unit: newton per coulomb (N/C)
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______________from the positive and
____________the negative
In the direction a positive charge would travel
in the field
Spacing of lines show _____________________
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• Two formula’s:
E: electrical field (N/C)
F: force (N)
Q: charge (C)
k: constant (For air, k = 9.0 x 109 N·m2/C2)
d: distance (m)
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All charge lies on the _______________ of a
conductor
Electrical field inside a conductor is _______
E = 0 inside
conductor
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The metal outside the car gives the car a path
to the ground
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Here is more proof of shielding

_____________ occurs when the electric field
around a conductor becomes so strong. The
___________________ helping the charge make
a break for the ground.

Arc- a rapid discharge producing _______,
_________, and _________.
Electrical forces
• Lightning is caused by a giant
buildup of _________________.
• The cloud, air, and ground can act
like a _______________.
• All the accumulated ___________
__________ flow from the cloud
to the ground, _______________
along the path (to as much as
__________°C) so that it glows
like a bright streak of light.
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Charges are separated in storm clouds; + top
and – bottom
Ground under the cloud becomes
____________ charged by _____________
V = millions of volts; causes arc discharge
with tremendous ___________.
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Electric current is caused by __________________
_________________ .
Electric current comes from the motion of
____________________.
current

A capacitor is a __________________ for electric
charge.
 Capacitors can be connected in series or
parallel in circuits, just like resistors.
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A capacitor can be _____________ by connecting it to a
______________ or any other source of _________.
A capacitor can be ________________ by connecting it to
any ________________________that allows current to flow.
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Electric current is similar in
some ways to a current of
___________.
Like electric current, water
current can ____________
and do __________.
A waterwheel turns when a
current of water exerts a
____________ on it.
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An electric circuit is a _______________
through which electric _____________ travels.
A good example of a circuit is the one found
in an electric toaster.

__________ in electric circuits are similar in
some ways to _____________________that
carry water.

When drawing a _________________,
___________ are used to represent each part
of the circuit.

________________
are quicker and
easier to draw than
realistic pictures of
the components.

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A _____________ is an electrical device that
_________________carried by electric current in
a specific way.
Any electrical device that uses energy can be
shown with a ___________________.
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Draw the symbol used in diagrams for a
Wire
Battery
Light
Resistor
Switch
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Current only flows when
there is a __________
and unbroken path, or a
____________________.
Flipping a switch to the
“______” position creates
an ________________by
making a break in the
wire.
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Electric current is measured in units called
_____________________________for short.
One amp is a flow of a certain quantity of
_______________________________.
The amount of electric _________________a
circuit always equals the __________________
the circuit.
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Voltage is a measure of ____________________
___________, just like height is a measure of
gravitational potential energy.
Voltage is measured in __________________.
A voltage difference of 1 volt means 1 amp of
current does _____________________________.
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A difference in voltage provides the energy
that causes ___________________________.
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A useful meter is a
_____________________, which
can measure _________ or
_________, and sometimes
_____________.
To measure voltage, the
meter’s probes are touched
to two places in a circuit or
across a battery.
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A battery uses ___________
______________to create
the voltage difference.
Three 1.5-volt batteries
can be stacked to make a
total voltage of __________
in a flashlight.
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A pump is like _________________ because it
brings water from a position of low energy to
high energy.

If you want to measure
current you must force
the current to pass
_______________________.

Water
meter
measuring
water flow
Multimeters can
measure two types of
current: alternating
current ________ and
direct current _________
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Circuit breakers and fuses are
two kinds of devices that ________
______________________________by
making a break that stops the
current.
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Resistance is the
measure of how
strongly an object
______________________
through it.
The relationship
between electric
current and resistance
can be compared with
water flowing from the
open end of a bottle.

The total amount of resistance in a circuit
____________________________________ in the
circuit for a given voltage.
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Electrical resistance is measured in units
called ___________.
This unit is abbreviated with the Greek
letter _______________
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The current in a circuit depends on voltage
and resistance.
Ohm’s law relates _______________________
_____________________ with one formula.
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If you know two of the three quantities, you
can use Ohm’s law to find the third.

Every electrical
device is designed
with a resistor that
causes the right
amount of current to
flow when the device
is connected to
voltage.
A
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The resistance of many
electrical devices varies
with ____________ and
________________.
A light bulb’s _________
_________________when
there is ________________
because the bulb gets
hotter when more current
passes through it.