Science Flashcards
(33 cards)
Electricity
Is a form of energy
Produced by the movement of
electrons
It flows through paths or electric
circuits
Electrons travel through these
paths; provided the path is not
ELECTRIC CURRENT
Most devices we use at home, work, and
school use some form of electric current
They are dependent on electricity that
flows from an energy source through
conductors (wires) to the devices and
back again
The flow of electricity through a
conductor on a closed path is called
electric current
Because the electrons flow in only one
direction, this is called direct current
The wires and device resist the flow of
electrons, like a partial clog in a water
pipe
BATTERY- DIRECT CURRENT
The most common source of electricity for
powering small electrical devices
Chemical reactions inside the battery energize the
electrons as they move from the cathode (positive
terminal) to the anode (negative terminal)
The electrons must move through an external circuit
(the device) in order to get back to the cathode
Because the electrons flow in only one direction,
this is called direct current
ALTERNATING CURRENT
Electrical energy is produced at power generating stations and
transmitted via power lines and wires
The current in these wires flows back and forth in both
directions, or alternates
It can reverse itself 60 times each second!
Alternating current is the type of electricity used in our
homes, schools, and other buildings
Closed circuit Open circuit
An unbroken electron path through
which electrons are moving
An electrical path having a break in
it; electrons do not flow through
ALL CIRCUITS MUST CONTAIN 3 THINGS:
1.
Conductor
A device that allows electricity to
pass easily through it
Example: wire
2.
Energy Source
Source that gives the circuit its
energy
Example: battery
3.
Load
A device or appliance which uses
the energy
Example: light bulb
An 4th optional device- Switch to
control the flow of electrons.
Schematic Diagram
A schematic diagram is a
diagram that uses symbols to
represent a set-up like a
circuit.
**Circuit Symbols- refer
to- Activity Circuit Diagram
Symbols*
Electric current
The flow of electrons around
an electric current
Electric current is measured in
amperes(A)
An ammeter is a device used
to measure current
Potential difference or Voltage
The force that pushes electrons
through a circuit
Measured in volts (V)
A voltmeter is a device which
measures potential difference
Resistance
The measure of how easily current can
flow through a material
It is measured in ohms ( Ω )
An ohmmeter is a device used to
measure resistance
A material that is difficult for electrons to
flow through is called a resistor
Kind of circuits
Series Circuit
A circuit that provides only one path for electrons to flow
Parallel Circuit
A circuit providing many paths for electron flow
Potential Difference (Voltage)
Potential energy is the
energy stored in an
object.
A battery has chemical
potential energy in the
electrolyte.
Chemicals in electrolytes
react with the electrodes
which then causes an
difference in the amount of
electrons between the two
terminals.
One terminal has mainly negative charges and
the other terminal has mainly positive charges.
If a conductor is connected to both terminals,
then the electrons flow from the negative
terminal to the positive terminal.
The difference in electric potential energy between two
points is called the potential difference or voltage (V).
It is this difference between two points that causes
current to flow in a closed circuit.
The higher the potential difference in a circuit, the
greater the potential energy of each electron.
Measuring Potential Difference
(Voltage)
The potential difference
is measures with a
voltmeter.
The SI unit for measuring
potential difference is the
volt (V).
How Electrons Transfer Energy in a
Circuit
How do the electrons get from the switch to the
light bulb so fast?
When an energy source is connected to a
circuit, electrons in the conductor “push” or
repel other electrons nearby.
Current
Electric current is a measure of the amount of
electric charge that passes by a point in an
electrical circuit each second.
There are two types of electric current:
Direct Current (DC)
Alternating Current (AC)
Current that flows in
one direction is called
direct current (DC)
The flow of current
from a battery is DC.
Alternating current (AC) flows back and forth at regular intervals called
cycles.
The flow of current from an external electrical outlet is (AC).
This current comes form generators and is carried by the big power lines
to your home.
Measuring Current
Current is measured using
an ammeter.
The unit of electric current
is the ampere (A).
An ampere is a measure of
the amount of charge
moving past a point in the
circuit every second.
Current Electricity and Static Electricity
Current electricity is the flow of electrons in a
circuit through a conductor.
Static electricity is the electric charge that
builds up on a surface of an object.
Static electricity discharges when it is given a
path, but it does not continue to flow.
Electrons Flow and Conventional Current
Current, in terms of electrons, flows from a
negative terminal to a positive terminal in a
battery.
In conventional current
the movement of
electrons in a circuit
flows from the higher or
more positive source to
the lesser or more
negative source.
Resistance
Resistance is the degree to which a substance
opposes the flow of electric current through it.
Resistance is measured in ohms.
Conductors allow electrons to flow freely through them
and have low resistance values.
Insulators resist electron flow greatly and have high
resistance values.
When a substance resists the flow of electrons, it slows
down the current and converts the electrical energy
into other forms of energy.
The more resistance a substance has, the more energy
it gains from the electrons that pass through it.
The energy gained by the substance is radiated to its
surroundings as heat and/or light energy.
greater resistance to electron flow
slower current (component is less conductivity)
electrical energy converted into other forms of energy
Resistance in Circuits
Example:
Filament in a light bulb is
a resistor.
The filament’s high
resistance to the
electron’s electrical
energy causes it to heat
up and produce light.
Resistors and Potential Difference
Electrons have a higher potential difference as
they enter a resistor compared to when they
leave a resistor.
Electrons’ entering a
resistor is where the
potential energy is greater.
Electrons’ leaving the
resistor is where potential
energy has been converted
to another form of energy.
Types of Resistors
Resistors come in many
shapes and sizes
The type of material
the resistor is made
form affects its
resistance.
Resistance in a Wire
Water in a Pipe Model:
Resistance in a pipe reduces
the flow of water.
The smaller the pipe the
greater the resistance, so
the flow is less.
Resistance in a conductor
reduces the flow of
electrons.
