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Science > chapter 11(electrical circuits) > Flashcards

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
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2
Q

Cells and Batteries

A

All electric circuits contain a
source, conductor, a load,
and a control.

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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
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4
Q

TERMINAL

A
  • location on a cell
    that must be
    connected to
    other components
    to form a circuit
  • positive and
    negative terminals
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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.
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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.
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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.
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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.
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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.
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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.

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11
Q

WIRE

A
  • conductor that joins different circuit
    components
    – e.g. metal (aluminum, copper) wire coated with
    plastic or rubber insulator
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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)
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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
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14
Q

ELECTRIC CIRCUIT

A
  • Closed (complete)or open (incomplete)
    circuits
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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.
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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.

Science (14 decks)

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