P2- current + components Flashcards
what is electric current?
flow of electrical charge.
what makes a circuit flow
closed circuit (completed) and source of potential difference
what is resistance?
anything that slows the flow down
what factors effect resistance?
series, parallel circuit
length of wire
what does the GRAPH of a OHMIC CONDUCTOR it look like?
LINEAR (straight line)
because it is a constant tempature
what does the GRAPH of a FILAMENT LAMP it look like?
NON-LINEAR
curve at start and end
because as current increases so does the temperature (not constant)
what does the GRAPH of a DIODE it look like?
NON-LINEAR
only flow one direction,
flat lines before it has rapid increase
what is an LDR
BIRD
brightness increase, resistance decrease
what is a thermistor
temperature dependant resistor,
-when hot resistance drops
-cool conditions = high reistance
what is a sensing circuit?
turn on or increase power to components depending on conditions,
this is when thermistors or LDRs may be used
describe series circuit
-one pathway
-current is same everywhere
-voltage split/shared between components
-increased resistors means overall resistance decreases
describe parallel circuit
-multiple pathways
-current split branches
-voltage same everywhere
-increased resistor = overall resistance decreases
what does the LIVE wire do? and what does it look like?
-brown
-provides alternating pd at 230v from main supply
what does the NEUTRAL wire do? and what does it look like?
-blue
-completes circuit
what does the EARTH wire do? and what does it look like?
-green + yellow
-safety feature: stop from becoming live by creating a path for current to flow to ground (prevents electric shock)
what is the role of the fuse?
contains thin wire which HEATS up + MELTS if too MUCH CURRENT passes through it. if this happens we say “the fuse has blown”
what is the national grid?
-range of different power stations
-interconnected by high voltage transmission lines
-power supply can balance demand over the whole country
What is the power station? and it’s voltage supply?
-generate electricity that is transported around country
-25KV
What is a pylon? and it’s voltage supply?
supports electricity cables
132KV
What is the voltage supply of the consumer?
230kv
what is a transformer
increases and decreases voltage at different stages at the national grid
Why is the current low when transporting across national grid?
high current means cables get hot and alot of energy wasted on thermal energy making it inefficient. a low current means the voltage must be high. A step-up transformer decreases current and increases voltage. This makes the national grid effiecent as it reduces amount of energy wasted.
what is OHMS law ?
-current flowing through a resistor is directly proportional to voltage
-current across a resistor is inversely proportional to resistance
what is a direct current?
constantly flowing same direction
what is alternation current?
changes direction multiple times per sec, depending on frequency supply
