639860
Description
Mind Map by Henry Kitchen, updated more than 1 year ago
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Created by Henry Kitchen
about 10 years ago
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Currents in
Electrical Circuits,
AQA P2.3
- Build up of static
electricity is caused
by friction
- When certain insulating
materials are rubbed
together, negatively
charged electrons will be
scraped off one material
and dumped on the other
- This leaves a positive
static charge on one
and a negative charge
on the other.
- Which way the electrons
are transferred depends
on the two materials
involved
- Electrically charged
objects attract small
objects placed near
them
- The classic examples are
polythene and acetate rods
being rubbed with a cloth
duster, as shown in the
diagram
- The classic examples are
polythene and acetate rods
being rubbed with a cloth
duster, as shown in the
diagram
- Electrically charged
objects attract small
objects placed near
them
- Which way the electrons
are transferred depends
on the two materials
involved
- This leaves a positive
static charge on one
and a negative charge
on the other.
- When certain insulating
materials are rubbed
together, negatively
charged electrons will be
scraped off one material
and dumped on the other
- Positive and negative
electrostatic charges are only
ever produced by the
movement of electrons
- A positive static charge is always
caused by electrons moving away
elsewhere. The material that loses the
electrons loses some negative charge
and is left with an equal positive
charge.
- A positive static charge is always
caused by electrons moving away
elsewhere. The material that loses the
electrons loses some negative charge
and is left with an equal positive
charge.
- When two charged objects are
brought together, they exert a force
on each other. These forces
decrease in strength was the
distance between the two things
increases.
- Opposite charges are
attracted to each other
- Identical charges repel
each other
- Opposite charges are
attracted to each other
- Charges can move
easily through
conductors. Metals are
good conductors.
- Current is the flow
of electric charge
round a circuit.
Current will only flow
if there is a potential
difference (voltage)
across a
component. Unit:
Amperes, A.
- Potential
difference is
the driving
force that
pushes the
current
around. Unit:
Volts, V.
- Potential difference is the work
done (the energy transformed in
joules) per coulomb of charge
that passes between two points.
It is given by the following
formula: Voltage = work
done/charge. Voltage and
potential difference are
interchangeable terms.
- Potential difference is the work
done (the energy transformed in
joules) per coulomb of charge
that passes between two points.
It is given by the following
formula: Voltage = work
done/charge. Voltage and
potential difference are
interchangeable terms.
- Resisitance
is anything
in a circuit
which slows
the flow of
current
down. Unit:
Ohm, Ω.
- The greater the
resistance across a
component, the
smaller the current
that flows (for a
given potential
difference across
the component).
- Total charge through a
circuit depends on current
and time.
- Current is the rate of flow of charge. When current (I)
flows past a point in a circuit for a length of time (t)
then the charge (Q) that has passed is given by this
formula, with current being measured in Amps,
charge in Coulombs and time in seconds::
- The greater
the current, the
greater the
charge flowing.
- Current is the rate of flow of charge. When current (I)
flows past a point in a circuit for a length of time (t)
then the charge (Q) that has passed is given by this
formula, with current being measured in Amps,
charge in Coulombs and time in seconds::
- Ammeters must be
placed in series, while
voltmeters must be in
parallel.
- Difference-Current graphs
- Resistance increases as heat increases
- This is because heat energy causes
ions in conductors to vibrate more,
making it more difficult for
charge-carrying electrons to get through
conductors - the current can not flow as
easily with high resistances
- This is because heat energy causes
ions in conductors to vibrate more,
making it more difficult for
charge-carrying electrons to get through
conductors - the current can not flow as
easily with high resistances
- YOU MUST KNOW OHM'S LAW!!!
- Diodes are made of
semiconductor materials
such as silicon and have
low resistance in the
'forward' direction and very
high resistance is the
'reverse' direction
- Types of resistor
- Carbon film - obvious
- Wire-wound -
made of coils
of resistive
wire
- Variable - can be
set at different
values
- LDR - high
resistance in
darkness and
vice versa
- Thermistors -
high resistance at
low temperatures
- Carbon film - obvious
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