673055
P5 - Electric Circuits
- Static Electricity
- some insulating materials can become
electrically charged when rubbed
against each other, the electrical
charge then stays in the material. it
doesn't move - the charge is STATIC
- charge builds up when electrons
(with a negative charge) are
rubbed off one material onto
another.
- the material receiving the electrons
becomes negatively charged and the one
giving up the electron will become positive
charged.
- if a perspex rod is rubbed with
cloth, the rod will lose electrons
and then become positively
charged. the cloth gains electrons
to become negatively charged.
- if an ebonite rod is rubbed with fur, the rod
gains electrons to become negatively charged,
he fur loses electrons to become positively
charged
- the material receiving the electrons
becomes negatively charged and the one
giving up the electron will become positive
charged.
- charge builds up when electrons
(with a negative charge) are
rubbed off one material onto
another.
- some insulating materials can become
electrically charged when rubbed
against each other, the electrical
charge then stays in the material. it
doesn't move - the charge is STATIC
- repulsion and attraction
- when 2 charged materials are
brought together, they exert a
force in each other so they are
either attracted or repelled.
- 2 materials with the same type
of charge will repel each other.
but, two materials with different
charges will attract each other.
- if a positive rod is moved near
another positively charged rod on a
string, the suspended rod on the
string will be repelled. the same will
happen with 2 negatively charged
ebonite rods.
- if a negatively charged rod is
mode near to a positively charged
suspended perspex rod, the
suspended perspex rod ail be
attracted - the same would happen
if the rods were the other ways
around,
- if a positive rod is moved near
another positively charged rod on a
string, the suspended rod on the
string will be repelled. the same will
happen with 2 negatively charged
ebonite rods.
- 2 materials with the same type
of charge will repel each other.
but, two materials with different
charges will attract each other.
- When a car is spray painted, a panel of the
car is positively charged and the paint is
negatively chafed. the paint particles repel
each other but are attracted to the positively
charged panel. this will cause the paint to
be applied evenly
- when 2 charged materials are
brought together, they exert a
force in each other so they are
either attracted or repelled.
- electric circuits
- an electric current is a flow
of charge, measured in
AMPERES (AMPS)
- In an electric circuit, the components
and words are full of charges that are
free to move. when a circuit is made, the
battery causes these charges to move in
a continuous loop. the charges are nit
see up
- In an electric circuit, the components
and words are full of charges that are
free to move. when a circuit is made, the
battery causes these charges to move in
a continuous loop. the charges are nit
see up
- in metal conductors there
are lots of charges free to
move. insulators however
have few charges that are
free to move.
- metals contain a free electron in their
structure. the movement of these
electrons creates the flow of charge -
an electric current,
- metals contain a free electron in their
structure. the movement of these
electrons creates the flow of charge -
an electric current,
- the amount of current
flowing in a circuit depends
on the resistance of the
components in the circuit
and the POTENTIAL
DIFFERENCE across them
- Potential difference tells us the
energy given to the charge and is
another name for VOLTAGE. i is
essentially a measure od the push of
the battery on the charges in the
circuit.
- for example, a 12 volt battery will
transfer 12 joules of energy to every
unit of charge. a potential difference of
3 volts across a bulb means that the
bulb is transferring 3 joules of energy
from every unit of charge - this energy is
transferred as heat and light.
- for example, a 12 volt battery will
transfer 12 joules of energy to every
unit of charge. a potential difference of
3 volts across a bulb means that the
bulb is transferring 3 joules of energy
from every unit of charge - this energy is
transferred as heat and light.
- Potential difference tells us the
energy given to the charge and is
another name for VOLTAGE. i is
essentially a measure od the push of
the battery on the charges in the
circuit.
- the greater the potential difference -
voltage - across a component, the
greater the current that flows through the
component. two cells together provide a
bigger potential difference across a lamp
than one cell. this will make a bigger
current flow.
- 2 types:
- parallel circuits
- series circuits
- parallel circuits
- an electric current is a flow
of charge, measured in
AMPERES (AMPS)
- Resistance
and Current.
- components such as resisters, lamps
and motors resist the flow of charge
through them - they have resistance
- work is done by the power supply
and energy is transferred to the
component.
- the grater the resistance of a
component(s) the smaller the current that
flows for a particular voltage. or, the
greater the voltage needed to maintain a
particular current.
- even the connecting wires in
the circuit have some
resistance, it is usually
ignored because it is so small
- 2 lamps together in a
circuit with one cell have a
certain resistance.
including another cell in the
circuit provides a greater
potential difference. as a
result, a greater current
flows.
- adding resisters in series increases
the resistance as the battery has to
push through all the resisters.
- adding resisters in parallel
reduces the total resistance
and increases the total current
because this provides more
paths for the charges to flow
along.
- when an electric current flows through
a component, it causes the component
to heat up. in a filament lamp, this
heating effect is large enough to make
the filament to glow in the lamp.
- as the current flows, the
moving charges collide
with the vibrating ions in
the wore, giving them
energy - this increase in
energy causes the
component to become hot.
- as the current flows, the
moving charges collide
with the vibrating ions in
the wore, giving them
energy - this increase in
energy causes the
component to become hot.
- when an electric current flows through
a component, it causes the component
to heat up. in a filament lamp, this
heating effect is large enough to make
the filament to glow in the lamp.
- adding resisters in parallel
reduces the total resistance
and increases the total current
because this provides more
paths for the charges to flow
along.
- adding resisters in series increases
the resistance as the battery has to
push through all the resisters.
- 2 lamps together in a
circuit with one cell have a
certain resistance.
including another cell in the
circuit provides a greater
potential difference. as a
result, a greater current
flows.
- even the connecting wires in
the circuit have some
resistance, it is usually
ignored because it is so small
- the grater the resistance of a
component(s) the smaller the current that
flows for a particular voltage. or, the
greater the voltage needed to maintain a
particular current.
- work is done by the power supply
and energy is transferred to the
component.
- Resistance which is measured in ohms
is a measure of how difficult it is to get
a current through a component at a
particular potential difference or
voltage. the formula for it is;
Resistance = voltrage/ current
- current
voltage
graphs:
- as long as the temperature of the resistor stays
constant, the current through the resistor is directly
proportional to the voltage across the resistor,
regardless of which direction the current is flowing - if
one doubles, the other also doubles.
- as long as the temperature of the resistor stays
constant, the current through the resistor is directly
proportional to the voltage across the resistor,
regardless of which direction the current is flowing - if
one doubles, the other also doubles.
- The resistance of some materials depends
on ENVIRONMENTAL conditions.
- the resistance of a
thermistor depends on its
temperature. its resistance
will decrease as the
temperature increases -
allows more current to flow,
- The resistance of a light
dependant resistor (LDR)
depends on light intensity. its
resistance decreases as the
amount of light falling on it
increases - allows more current
to flow.
- as the resistance of a
LDR and a thermistor
can change, this will
result in a change in
the potential difference
for all the other
components in the
circuit.
- the resistance of a
thermistor depends on its
temperature. its resistance
will decrease as the
temperature increases -
allows more current to flow,
- potential
difference
and
current
- the potential difference
across a component in a
circuit is measured using a
voltmeter in volts, connected
in parallel across the
component.
- the current flowing
through a component
in a circuit is measured
in amperes (amos) (A)
using an ammeter
connected in series.
- when batteries are added in
series, the total potential
difference i the sum of all
individual potential
differences.
- when batteries are added in
series, the total potential
difference i the sum of all
individual potential
differences.
- when batteries are added in parallel, the total potential
difference and current through the circuit remains the
same but, each battery supplies less current - sharing the
load = longer lasting batteries.
- the current flowing
through a component
in a circuit is measured
in amperes (amos) (A)
using an ammeter
connected in series.
- the potential difference
across a component in a
circuit is measured using a
voltmeter in volts, connected
in parallel across the
component.
- components such as resisters, lamps
and motors resist the flow of charge
through them - they have resistance
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