ELECTRICITY
• Everything around you contains electric charges.
You aren’t
aware of the charges until you make them move from their
normal position.
• When these charges are forced to move the material has
become “charged” with “electricity”.
STATIC ELECTRICITY
AN IMBALANCE OF CHARGE ON
THE SURFACE OF AN OBJECT
THAT STAYS IN THE SAME
PLACE.
RECALL THE STRUCTURE OF THE ATOM…
• Positive particles called _____________ and
neutral particles called ___________ are
found inside the ________________. These
particles do not move easily in and out of the
nucleus.
•
Negative particles called ______________
are found in _________________
surrounding the nucleus. These particles can
move from one atom to another.
ELECTRICAL CHARGES
•
If an atom gains electrons it becomes • Electrical charges result from the
____________ charged. (There are
movement of __________ and not
more “” particles than “” particles)
from ______________ or
• If an atom loses electrons it becomes
_____________ charged.
• (There are not enough “” particles)
• If an atom has equal protons and
electrons it is ____________ .
______________ .
CHARGING BY FRICTION
• Charging by friction occurs
when two different neutral
objects are rubbed
together and electrons are
transferred from one
object to another.
DETERMINING CHARGE
• The object with the weakest hold on its
electrons transfers them to the other
object and becomes positively charged.
• The object with the stronger hold on its
electrons gains them from the other
object and becomes negatively charged.
• See page 473
PREDICT THE CHARGE…
• When a rubber rod is rubbed with
Fur…
Rubber has a stronger hold on its
electrons and gains electrons from the
fur
This makes the rod negatively charged
and the fur positively charged.
PREDICT THE CHARGE…
• When a glass rod is rubbed with
silk…
The silk has a ______________
hold on its electrons, becoming
_____________ charged.
The glass rod has a ____________
hold on its electrons becoming
______________ charged.
YOU MOVE ME ACTIVITY
LAW OF ELECTRIC CHARGES
•Like charges – repel
•Unlike charges – attract
•Charged objects attract
neutral ones
INDUCED CHARGE SEPARATION
• Neutral objects are attracted to
charged objects due to induced
charge separation.
• A shift in the position of electrons
in a neutral object when a charged
object is brought near
• Sometimes called polarizing the
molecules
DETECTING CHARGE
• Scientists can detect the presence of
electric charges using an electroscope.
• Pith ball electroscope – detects the
presence of a charge by moving
towards a charged object.
• Metal-leaf electroscope – detects the
presence of charge by causing the
leaves to spread apart.
CHARGING BY CONTACT
• When two objects of different
charge are touched together,
electrons are transferred from
one object to the other.
• This results in two objects with
the same charge.
CHARGING BY CONTACT
• A charged object can only
charge a neutral object if:
•
the neutral object is a
conductor
• if the neutral conductor is
supported by an insulator
LET’S INVESTIGATE!
CHARGING POSITIVELY BY CONTACT
CHARGING NEGATIVELY BY CONTACT
THINGS TO REMEMBER…
• When charging by contact:
• The objects must touch each other.
• The objects will have the same charge.
• The originally charged object will become a little less charged.
TIME TO WORK!
• Page 471 # 4-9
• Page 477 # 1, 2, 5, 6, 8
VAN DER GRAAF GENERATOR
• A metal sphere is supported on an
acetate stand.
• Inside a rubber belt turns against a
metal brush, charging the sphere by
friction.
• Static charge is transferred to you
when you touch the metal sphere.
CHARGING TEMPORARILY
• A charged object is brought
next to but not touching a
neutral object.
• The electrons move either
towards or away from the
charged object creating a
temporary charge on one
side of the neutral object.
• Induced Charge Separation
CHARGING PERMANENTLY
CHARGING PERMANENTLY
TIME TO WORK!
• Page 489 # 2, 3, 4, 6
INSULATORS AND CONDUCTORS
• Conductors are materials that
allow electrons to move through
them.
• Insulators are materials that
inhibit or prevent the movement
of electrons.
• Resistors are a mixture made up
of conductors and insulators
GROUNDING
• The excess charge on an object can
be removed by grounding the
object.
• Grounding involves connecting an
object to a large body, like Earth,
that is capable of absorbing the
charge and effectively remaining
neutral itself.
USING PAGE 480-481…
Conductors
Insulators
Resistors
TIME TO WORK!
• Read pg 480-482 and answer
pg 482 # 2, 3, 6, 7
• Read pg 492-495 and answer
pg 495 # 1, 2, 4