resistance/circuits/wires/electronics Flashcards
how can you calculate resistance
R = V
-
I
r=resistance
V=potential difference
I=Current
why do you need to add a resistor
to make sure the the light isn’t too bright
what happens to the current when you increase the potential difference on a graph
there is a straight line passing through 0
showing that the current through a resistor is directly proportional to the potential difference and the resistance is constant
what must stay constant for the resistance to stay constant
temperature
what is a convenstional current
drawing the current from the opposite direction
what is a current
an electrical current is a flow of charge around a circuit
how can you measure the potential difference
volt meter
what is a ldr
light-dependent resistor
what happens to the resistance in a light and dark environment to a ldr
in light intense areas the ldr have low resistance
in dark intense areas the ldr has high resistance
name a way a ldr can be used
to turn of the screen of a mobile phone when yo are on a phone call with someone
what does a thermistor
the resistance of a thermistor decreases if the temperature increases
what happens to the resistance when the temperature is high or low
when the temperature is low the resistance is high
when the temperature is high the resistant is low
where can a thermister be used
in a pc to turn on the fan when it heats up
what is an alternating current
the flow of electrons moves forwards and in a reverse directions
how are electrical appliances connected in the uk
uses a 3 core cable
what is the blue wire
neutral- completes circuit potential difference = 0V
compared to the live wire
what is the green/yellow striped wire
earth wire- safety wire to stop appliances from becoming live
how does the earth wire work and what does it prevent
earth wire is connected to the ground if the case becomes ive a huge amount current flows to earth. The fuse melts and shuts of the current which prevents electric shocks
why is the live wire dangerous
can be easily touched and still has 230 V in it and would transfer to the person and they could be electrocuted
why can appliances with metal casing be dangerous
if the live wire comes loose and touches the metal case the case can come live ad have a current in it
