Chapter 6 – Electricity
6.1 Electric Charge
Positive and Negative Charges
Atoms
• Matter is composed of _______
• Atoms are composed of protons, neutrons and
electrons
• The amount of positive charge on a proton is _____
equal to
the amount of negative charge on an electron
• Atoms have _______________
no electric charge (electrically neutral)
• Amount of electric charge is measured in coulombs
________ (C)
6,250 million billion protons in 1 C of electric charge
6,250 million billion electrons in -1 C of electric charge
Coulomb's Law: Like charges _____
repel and opposite
attract
charges _______.
• The difference between the # of protons and
the # of electrons determines an object’s
electric charge therefore
___________;
more electrons.
(-) charged obj. have ______
fewer
(+) charged obj. have ______electrons.
transfer electrons.
Obj. are charged by the _______of
Transferring Charge
• Electrons are
bound more tightly to
_______________
some atoms and
molecules than others
• Some atoms can
transfer
_______electrons
more
easily than others
• Leads to an buildup of
electrons on other
substances (excess
negative charge)
Static electricity
 _____________
STATIC ELECTRICITY
Law of Conservation of Charge
Charge can be transferred
_________ from object to object,
destroyed
cannot be _______or
created _________
but it _______
Charges Exert Force
The force between electric charges depends on
Distance
• ________between
charges
Amount
• ________of
charge
Mass
• _____
Gravitational
Forces have similar properties.
_______________
On this scale gravity dominates!
Comparing Electric Forces and Gravitational
Forces
weaker than electric
• Force of gravity is much ______
force
– Electric force between a proton and an electron
in a hydrogen atom is about a thousand trillion
trillion trillion times larger (1039 X) than the
gravitational force between the same particles.
• Chemical bonds in molecules are due to
electrical forces between atoms
_______
gravitational forces
– Much larger than the ___________
between the atoms
force dominates!
On this scale electrical
___________
Electric Fields
• Surround every electric charge and exerts the force
attracted
that causes other electric charges to be _________
repelled
or ________.
touching to exert force on each
• Do not need to be ________
other
• Any charge that is placed in an electric field will be
pushed or _______
pulled by the field
______
Electric Field Near Negative Charge
Electric Field Near Negative Charge
Conductors and Insulators
Conductor
electrons move easily
• Material through which ____________________
metals
• Best electrical conductors are ________
low resistance?
• Conductors have _____
Insulator
not able to move easily
• Material in which electrons are ____________________
tightly to atoms that make up
• Electrons are held ______________
insulators
glass , ______
plastic , rubber
• Best insulators are _____
______ and
ceramic
________.
high resistance
• Insulators have a _____
Conductors and Insulators
Types of Charging
Charging by Contact
Charging by Induction
The process of transferring
charge by _________
touching or
________.
rubbing
• Also called charging by
conduction
___________
rearrangement of
The _______________
electrons on a _________
neutral
object caused by a _______
nearby
object
Lightning
6.1 Summary
• 2 types of electric charges are (+) & (-).
• Like charges repel, unlike charges attract.
• On molecular level, electric force is stronger than
gravitational force
• Electric force acts through electric fields.
• Electric fields surround charged objects. Any
charged object that enters a region with an electric
field experiences an electric force.
• Electrons move easily through conductors
• Electrons do not move easily through insulators
6.2 Electric Current
Current and Voltage Difference
Electric current the net movement of electric
• ________________:
charges in a single direction
amperes (A)
• Measured in _________
1 Coulomb of electric charge
• 1 ampere = __________________________
• A voltage causes charges to move, which in turn
produces a current
_______.
closed for a current to be produced.
• A circuit must be ______
A charged object has electric PE due to its
position in an electric field.
Potential difference or
________
voltage is the
difference in electrical
PE per unit charge.
– SI unit for pot. diff. (V) =
volts = 1Joule/coulomb
– Ex. 12V vs. 9V
higher voltage to
• Electric current is from _____
lower
_____voltage
• Voltage difference is related to the
force that causes electric charges to flow
_____________________________
volts (V)
• Voltage difference is measured in _____
_ _
_ _ _
_ _ _ _
_
_
_ _ _ _
_ _ _
_ _
_
_ _
_
Charge Flow
_
_
_
_
Current
Low Voltage
_
_
_
_ _
_
_
_
High Voltage
Electric circuit a closed path that electric
• ___________:
current follows
Current and Flow Direction
direction of the electric current is always
The _______
higher voltage to a _____
lower voltage, but …
from a _____
• The electrons
_______ in a circuit
_____actually flow from a
lower voltage to a _____
higher voltage
_____
Batteries
https://www.youtube.com/watch?v=CX84l5ZZHVg
Dry – Cell Batteries
Wet – Cell Batteries
• Consist of ___________
2 electrodes
surrounded by a material
electrolyte
called an ___________
charges
• Electrolyte enables ________
to move from one electrode
to another
Chemical reaction occurs
• _________________
when the 2 terminals are
circuit
connected in a ________.
Voltage difference between
• ________
these 2 terminals causes a
current through a
____________.
Closed ciruit
battery
• Example: Flashlight
_______________
• Contains
2 Connected plates made
_________________
metals or
of different _______
metallic compounds in
_________
electrolyte
an ___________
• The electrolyte is a
conducting
liquid solution
____________________
• Example: Car
__________
battery
Dry - Cell
Anode (negative)
Cathode (positive )
Wet - Cell
Resistance
Resistance
• ___________:
the tendency for a material to
resist the flow of electrons and to convert
electrical energy into other forms of energy
– Measured in ohms (
)
• Caused by _____________
internal friction which slows the
through conducting material
movement of charges
____________________________
A special type of
• Resistor: ______________
conductor used to
_______________________
______________________
control current.
Superconductor
• Certain metals and compounds that have
zero resistance when their temp. falls
_____
critical
below a certain temp called ______
temperature
__________.
Semiconductor
pure state are insulators
• Semiconductors in _________
________.
• However, as atoms/impurities are added, or
become compounds, these materials begin
conduct electric charge
to be able to ___________________.
Schematic
circuit
• Diagram or drawing used to build a _______.
• There are two types of circuits.
Series one path for electrons, if one bulb
– ________:
goes out they all do
Parallel more than one path for electrons, if
– _________:
one bulb goes out the rest can still shine
Schematic Symbols-Draw symbols
on the right side margin of notes
Series Circuit
Parallel Circuit
Open vs Closed Circuit
•
•
Closed
______circuit
allows electron to flow, lights on
Open circuit does not, lights off
______
Circuit Breakers and Fuses
• Too many appliances on at the same
time in a home cause the overall
resistance of the circuit to be
lowered.
– Result is a circuit carrying more
electrical current than is safe it is
___________
overloaded . Fires can result when
this happens.
Circuit breakers act as a switch and
– _______________
open the circuit.
Formulas
• SI unit for electric charge
Coulomb is the quantity of the electricity transported in
– _________
one second by the current of one ampere. Symbol: (C)
• Potential difference, voltage (V)
– 1Joule/coulomb (1J/C)
• Unit for Current (I) = Ampere (amp-A)
• Unit for Resistance (R) = Ohm Ω
– Formula : Resistance = Volts/Current
– Formula with symbols: Ω = V / I
• Unit for Electric Power (P) = Watts (Watts)
--- Formula: Power = Volts x Current
--- Formula with symbols: P= V x I
Amps vs volts: https://www.youtube.com/watch?v=9iKD7vuq-rY