Physics HT1
Straight lines on a circuit diagram indicate between
connections
components
what is a lamp symbol
a circle with a X
what is a voltmeter symbol
a circle with a V
what is a cell symbol
two lines one bigger than the other
what is a ammeter symbol
a circle with a A
The movement of electric is the basis of electrical current
charges
electric current is measured in
amps
a conductor is a material that
allows electricity to flow through it
an insulator is a material that
does not easily allow heat and/or electricity to pass through it
pd is measured in
volts
what instrument do you use to measure a potential difference
voltmeter
what instrument is used to measure current
ammeter
in equations energy (J) is
E
in equations power (W) is
P
in equations P.D (V) is
V
in equations current (A) is
I
in equations charge flow (C) is
Q
in equations time (s) is
T
which variables affect the size of a current
resistance
potential difference
what is resistance measured in
ohms (Ω)
resistance is a measure of the
difficulty of the flow of current through a current
if the resistance is increased the current will
decrease
if the potential difference is increased the current will
increase
to measure resistance you need
a voltmeter in parallel
an ammeter in series
ohm's law
a straight constant slope tells us that the resistance is
constant
we can plot a current-voltage graph by changing the potential difference across a circuit component and measuring the
current
a diode is a component that only allows current to flow through it in
one direction
the diode blocks the alternating current when it
changes direction
a light dependent resistor (LDR)s resistance changes with
light resistance
a thermistor is a component where resistance changes with its
temperature
what is a thermistor symbol
a rectangle with a line passing through
what is a LDR symbol
a rectangle with two arrows pointing at it
what effect does intense light have on a LDR
it increases the resistance
in an ohmic conductor, the resistance
remains constant
what are the three wires
live
neutral
earth
what colour is the neutral wire
blue
what colour is the live wire
brown
what colour is the earth wire
green and yellow
what does the live wire do
carries 230V
it provides the alternating potential difference from the mains electricity supply
what does the neutral wire do
it completes the circuit and carries current away from the appliance
what does the earth wire do
it has a 0V potential and only carries a current if there is a fault
it is a safety wire to stop the appliance becoming live
how much energy does a 50W bulb use per second
50J
all places electricity goes
power station
step-up transformer
national grid
step-down tranformer
homes
what does a step-up transformer do
a step up transformer at the power station steps up the voltage and consequently steps down the current
what does a step-down transformer do
step-down transformers convert high voltage power to a low voltage
what kind of appliance casing requires an earth wire
metal