chapter 11(electrical circuits) Flashcards
1
Q
ELECTRIC CIRCUIT
A
- a closed path along which electrons that are
powered by an energy source (e.g. cell or
battery) can flow - electrons return to
the energy source
2
Q
Cells and Batteries
A
All electric circuits contain a
source, conductor, a load,
and a control.
3
Q
ELECTRIC CIRCUIT
A
- To form a closed circuit, cells must be
connected to a circuit at their positive and
negative terminals. - electrons flow from
negative to
positive terminal
4
Q
TERMINAL
A
- location on a cell
that must be
connected to
other components
to form a circuit - positive and
negative terminals
5
Q
Voltaic Cells
A
- The first voltaic cells
were constructed
around 1800 by
Alessando Volta, an
Italian physicist, who
stacked alternating
discs made of silver
and zinc, separated by
pieces of cloth soaked
in salt water.
6
Q
Voltaic Cells
A
- Voltaic cells represent a source of
energy that generates an electric
current by chemical reactions
involving two different metals or
metal compounds separated by a
conducting solution. - Electrodes are the two metal
terminals found in a cell or battery. - Anode (-ve terminal) is an
electrode through which electric
current flows out of the cell and into
a polarized electrical device. - Cathode (+ve terminal) is an
electrode through which electric
current flows out of the device and
back into the cell.
7
Q
Cells, Batteries, and Potential Difference
A
- the potential difference generated by a cell is limited to a few
volts because of the metals that are used for the electrodes - when a larger potential difference is required to operate a
motorized toy or the starter motor on a car, several cells are
connected in series (+ve terminal to –ve) to make a battery - e.g. 12 V car battery = six 2 V lead-acid cells
- potential difference across a battery of cells in series is the
sum of the potential differences across each cell.
8
Q
Types of Cells
A
- Dry cells are cells with an electrolyte that is a
paste. - Wet cells are cells with a liquid electrolyte.
Most wet cells use a solution of sulphuric acid
(H2
SO4
) as their electrolyte. - A primary cell can only be used once then
must be discarded (see Table 11.1 p.441). - A secondary cell can be recharged by passing an
electric current in the opposite direction through the
cell from another source. - This reverses the chemical reactions that occur in the
cell and restore it to full capacity.
9
Q
Fuel Cells
A
- Fuel cell cars and trucks combine hydrogen and oxygen to
produce electricity, which runs a motor. - Converting hydrogen gas into electricity produces only
water and heat as a byproduct, meaning fuel cell vehicles
don’t create tailpipe pollution when they’re driven.
10
Q
Solar Cells
A
- Solar cells are cells that convert sunlight into electrical energy.
When sunlight strikes a semiconductor such as silicon in a solar cell,
electrons are knocked loose from the atoms. - Solar cells can be used to power anything from calculators and
ornamental lights to homes, satellites, and even communities.
In October of 2009,
First Light 1, a 9.1
megawatt solar park,
opened in Stone
Mills, Ontario. The
first and largest solar
energy farm in
Canada covers an
area the size of 50
football fields.
11
Q
WIRE
A
- conductor that joins different circuit
components
– e.g. metal (aluminum, copper) wire coated with
plastic or rubber insulator
12
Q
SWITCH
A
- Switches are control devices (conductors) that
can complete or break the circuit to which it is
connected. - A switch is not required
for a circuit to operate. - Connecting wires
(conductors) join together
the circuit components
(eg. switch, bulb, battery)
13
Q
ELECTRIC CIRCUIT
A
- An open circuit contains a gap or break that
stops the continuous flow of electrons. - Any devices connected to
the switch (bulb) will stop
working. - If a bulb is loose and does
not contact the base or
the filament of an
incandescent bulb breaks
there is no flow of
electrons
14
Q
ELECTRIC CIRCUIT
A
- Closed (complete)or open (incomplete)
circuits
15
Q
Movement of Electrons NOT in a Circuit
A
- if a conductor wire is not
part of an electric circuit,
electrons move in
random directions,
colliding with electrons or
other ions - the electrons move
quickly but will not flow
in one direction along the
wire.
16
Q
Movement of Electrons in a Circuit
A
- chemical reactions in cell
cause charges to separate
(excess of electrons at -ve
electrode; deficit at +ve
electrode) - charge separation produces
electric field which moves
through circuit at speed of
light - electric field in completed
circuit causes electrons to
move in one direction (-ve
to +ve end) through wire
17
Q
ELECTRIC CURRENT
A
- The electric field produced when a cell is
connected to a circuit forces the free electrons to
move in one direction through the conducting
wire. - This produces an electric current.
- the rate (time) of movement of electric charge
- due to flow of electrons
- measured with an ammeter
- unit is amps, A
18
Q
ELECTRIC CURRENT
A
- flow of electrons along a specific path
- comes from generators, batteries (cells)
- e.g. in electrical appliances
19
Q
2) ELECTRICAL RESISTANCE
A
- property of a substance that hinders electric
current and converts electrical energy into other
forms of energy.
Model for Electrical
Resistance
* A marble (which
represents an
electron) collides
with pegs (which
represent the
metal ions in a
conductor).
* The electric field of
a cell makes
electrons move in
one direction.
20
Q
RESITOR
A
- a device used in an electric circuit to decrease the
current through a component by a specific
amount.
21
Q
LOAD
A
- a resistor or any other electrical device (e.g.
appliance) that transforms electrical energy into
heat, motion, sound, or light.
– e.g. filaments in incandescent light bulbs heat up emitting
light; heating elements in toasters, radios
22
Q
3) POTENTIAL DIFFERENCE (VOLTAGE)
A
- the difference in electric potential energy per
unit of charge (Coulomb) between two points in
a circuit. - often referred to as voltage.
- no such thing as voltage at a single point.
- e.g. when a charge flows through a flashlight
bulb, it enters the filament with a certain amount
of energy and exits with less energy
23
Q
2) POTENTIAL DIFFERENCE (VOLTAGE)
A
- measured with a voltmeter
- symbol is V
- unit is volts, V
24
Q
CIRCUIT DIAGRAMS
A
- uses standard symbols to represent the
components of an electric circuit. - This circuit contains a cell (1.5 V), a switch and
a bulb.
25
Q
Symbols for Specific Components
A
- Additional symbols you may see for circuit diagrams.
26
Q
1) SERIES CIRCUIT
A
- only one path along which electrons can flow.
– if you turn off one device then all devices will turn
off.
27
Q
Loads in Series
A
- As additional bulbs are added to the series,
the brightness decreases.
28
Q
Why do we use series circuits?
A
- Series circuits don’t
make sense for
home, schools or
factories but they do
have special uses - Parts of computers,
radios, and television
sets, space rockets
are wired in series
29
Q
2) PARALLEL CIRCUIT
A
- more than one path along which electrons can
flow.
– each appliance has its own path letting you shut off
one appliance at a time without affecting others
30
Q
Loads in Parallel
A
- When more loads are added,
the intensity of the existing
loads remains the same since
current increases with each
new load. - Brightness of the bulbs is
equal. - Loads can be disconnected,
and the other loads will
function.
31
Q
PARALLEL CIRCUIT
A
- 2 cells and 3 resistors in parallel, include
arrows to show the flow of electrons.
32
Q
SERIES & PARALLEL CIRCUITS
A
- A two cell (3V) battery with 4 resistors in series.
- A two cell (3V) battery with 4 resistors in parallel.
