I. OUTCOMES 1, 2 & 3 – STATIC ELECTRICITY & ELECTRIC CHARGES
I. OUTCOME 1: Electric charge = property that causes subatomic particles to attract or repel each other
A. Review: atomic structure!!!!
B. Charge is measured in units called Coulombs (C) C. Objects can have a positive or negative charge
D. Net charge = overall charge of an object, caused by an excess or shortage of electrons
1. More electrons than protons = negative charge 2. More protons than electrons = positive charge 3. Equal protons and electrons = neutral (no charge)
II. OUTCOMES 2: Charged Objects
A. Charged objects affect each other due to electrical forces 1. caused by attraction or repulsion of charges.
2. Like charges repel
Opposite charges attract
3. Force depends on the strength of charges and distance apart.
4. Electric field is the area in which one charged object can affect another (how far the force can reach).
B. Static Electricity = electrons move from one object to another creating a tiny imbalance in charge on an object.
~VERY tiny = less than one millionth of a Coulomb!
Ex. When you shuffle across the carpet, electrons move from carpet to your body This leaves each object slightly charged: Ex:
2. When you touch metal (a conductor), the excess electrons quickly move off your body = electric current = shock!
C. Electroscope = used to observe the force between charges.
1. Conductor – Something that electricity flows through easily.
2. In a conductor, electrons move freely and spread out evenly when possible.
3. Insulator – Something that has no free electrons, so it can’t carry current. 4. How the Electroscope works:
a) Negatively charged object (like a balloon) brought close to the metal. b) Electrons in the metal are repelled by the negative balloon, and move
away.
c) Top of metal is left slightly positive, foil “leaves” are both negative so repel each other.
III. OUTCOME 3: How Objects Become Charged
A. Charging by Contact: If you touch a negatively charged object to the
electroscope, some electrons will move to the electroscope giving it a negative charge.
~Can be used to test other charged objects
B. Charging by Friction: Rubbing a balloon on your head transfers electrons from your hair to the balloon, giving your hair a net positive charge and the balloon a net negative charge.
C. Polarization: When the positive and negative sides of atoms in an object line up in the same direction.
1) Negatively charged balloon causes electrons in the wall to move slightly away, to far side of atoms
2) Atoms of the wall are now polarized: one end positive, other end negative 3) Area of wall near the balloon has a slight positive charge, so is attracted to the balloon – it sticks!
D. Charging by induction: Using one object to charge another without changing the net force on the first object
I. OUTCOME 1:
Electric
charge
= property that causes
subatomic particles to
attract
or
repel
each other.
I.
OUTCOME 1: Electric charge
= property that causes subatomic particles to attract or repel each otherB. Charge is measured in units called
Coulombs
(C)
Charge of 1 proton = + 1.6 x 10
-16Coulombs
Charge of 1 electron
= - 1.6 x 10
-16Coulombs
B. Charge is measured in units called Coulombs (C)
C. Objects can have a
positive
or
C. Objects can have a positive or negative charge
D.
Net charge
= overall charge of
C. Objects can have a positive or negative charge
D. Net charge = overall charge of an object, caused by an excess or shortage of electrons
1. More electrons than protons =
negative charge
2. More protons than electrons =
positive charge
3. Equal protons and electrons =
II. OUTCOMES 2: Electrically
Charged Objects
II. OUTCOMES 2: Electrically Charged Objects
A. Charged objects affect each other due to electrical forces
1. Caused by attraction or repulsion
of charges.
2. Same charges repel
Opposite charges attract
+
+
-
+
-1. caused by attraction or repulsion of charges 2. Like charges repel
Opposite charges attract
3. Force to attract or repel depends
on the strength of charges and
distance the objects are apart.
Force is inversely
proportional to the
square of the distance.
So….
Double the distance –>
force decreases by a
Cut the distance in half –>
force increases by a
2. Like charges repel
Opposite charges attract
3. Force depends on the strength of charges and distance apart
4. Electric field is the area in which
one charged object can affect
4. Electric field is the area in which one charged object can affect another object(s) (how far the force can reach).
B. Static Electricity = electrons move
from one object to another creating
a tiny imbalance in the charge on an
object.
B. Static Electricity = electrons move from one object to another creating a tiny imbalance in charge on an object
~VERY tiny = less than one millionth of a Coulomb!
1. When two neutral objects rub
together, electrons move from one
to another.
Example: How Lightning becomes SHOCKING!
~VERY tiny = less than one millionth of a Coulomb!
1. When two neutral objects rub together, electrons move from one to another
Example: When you rub your feet
across the carpet, electrons move
from the carpet to your body
Ex. When you shuffle across the carpet, electrons move from carpet to your body This leaves each object slightly charged: Ex:
2. When you touch metal (a
conductor), the extra electrons
2. When you touch metal (a conductor), the extra electrons quickly move off your body = electric current = shock!
C. Electroscope = used to observe the force between charges.
1. Conductor – Something that
electricity flows through easily.
1. Conductor – Something that electricity flows through easily.
2. In a conductor, electrons move
2. In a conductor (something that electricity flows through easily), electrons move freely and spread out evenly when possible.
3. Insulator – Something that has
no free electrons, so it can’t carry
current.
3. Insulator – Something that has no free electrons, so it can’t carry current.
4. How the electroscope works:
a)Negatively charged object (like a
balloon) brought close to the
4. How the electroscope works:
a)Negatively charged object (like a balloon) brought close to the metal…
b)Electrons in the metal are
repelled by the negative balloon,
a)Negatively charged object (like a balloon) brought close to the metal…
b)Electrons in the metal are repelled by the negative balloon, and move away.
c)Top of the metal is left slightly
positive, foil “leaves” are both
c) Top of the metal is left slightly positive, foil “leaves” are both negative so they repel each other.
III. OUTCOME 3: How Objects
Become Charged
A. Charging by Contact: If you touch
a negatively charged object to the
electroscope, some electrons will
III. OUTCOME 3: How Objects Become Charged
A. Charging by Contact: If you touch a negatively charged object to the
electroscope, some electrons will move to the electroscope giving it a negative charge.
A. Charging by Contact: If you touch a negatively charged object to the electroscope, some
electrons will move to the electroscope giving it a negative charge. ~Can be used to test other charged objects
B. Charging by Friction: Rubbing a
balloon on your head transfers
electrons from your hair to the
balloon, giving your hair a net
B. Charging by Friction: Rubbing a balloon on your head transfers electrons from your hair to the balloon, giving your hair a net positive charge and the balloon a net negative charge.
C. Polarization: When the positive
and negative sides of atoms in an
object line up in the same direction.
C. Polarization: When the positive and negative sides of atoms in an object line up in the same direction.
When you put a charged balloon
on the wall, what happens?
1)Negatively charged balloon causes
electrons in the wall to move
1)Negatively charged balloon causes electrons in the wall to move slightly away, to far side of atoms
2)Atoms of the wall are now
2)Atoms of the wall are now polarized: one end positive, other end negative
3)Area of wall near the balloon has a
slight positive charge, so it is
2)Atoms of the wall are now polarized: one end positive, other end negative 3)Area of wall near the balloon has a slight positive charge, so is attracted to the
balloon – it sticks!
D. Charging by induction: Using one object to charge another without changing the net force on the first object
