P2 electricity Flashcards
what is current
the flow of electrons through
what is potential difference and its equation using current and resitance
it is the difference in electrical potential between two points.
potential difference= current x resistance
what is the equation for current charge and time
charge = current x time
what is resistance and the unit it is measured in
when electrical current degrades due to work being done on componants in the circuit
ohms
charcterisitics of an ohmic conductor
filament lamp
diode
ohmic conductor is constant and therefore the current is directly proportional to the resistance
filament lamp, everything increases
diode- current only flows through one direction therefore its graph only starts when the x axis is positive
how is potential difference distributed around a series circuit
and also a parallel circuit
series- its all shared
parallel- its the same across all componants
how is current distributed in
a series circuit-
a parallel circuit-
series- its the same across all componants
parallel- its all shared between branches
what is the equation linking power, potential difference and current
power= current x potential difference
what is the equation linking power current and resistance
power = current2 x resistance
what is the equation linking energy transfered, power and time
energy transfered= power x time
what do you do with any equation involving energy transfered
time the other two variables
what is direct current and what is alternating current
in alternating the current is constantly changing direction
what type of current is the uk mains supply and what is its voltage and its frequency
alternating current, 230v
50 cycles per second (50hz)
features of
live wire
neutral wire
earth wire
live- red and provides the alternating potential difference
neutral- blue and completes the circuit
earth- keeps it all safe by protecting the wiring
features of the national grid in terms of
type of current
how they cope with demand
high or low potential difference and current
alternating current
they have a high capacity to cope with a high demand
high potential difference and low current
what does a kettle do in terms of power
it transfers energy from the uk mains supply and turns it into its thermal energy store. its voltage is 230v
why does the national gird have high pd but not high current
- cheaper to have high pd
- high current would burn the wires
- lose loads of energy if current was high
how is static electricity caused
when insulating materials are rubbed together causing friction, all the negativlet charged electrons are dumped off one and put onto the other
how is a spark caused
as the potential difference increaes, the electrons try to escape, jumping and causing a spark
how do charged objects exert forces of attraction and repulsion from a distance
they have a charged electrical field
how is a negative electrical field represneted on a diagram
arrows point towards the object
how is a positivley charged electrical field displayed on a diagram
arrows point away from the object
what makes an electric shock happen
a large gap in potential difference and the transfer of electrons
process of investigating resistance in a series circuit
- set up circuit with ammeter and resistor
- measure current and then resistance using equation
- repeat this for 4 resistors then record your results and plot a graph on resistors and total resistance
list the steps required when investigating the affect of length on resistance
- attach two crocodile clips to a test wire (which is on a ruler) make sure theyre 10cm apart
- close the switch and record the current/pd to find resistance
- run this experiment a few times, making sure you increase the length of the wire by 10cm every time.
- plot your results in a graph measuring resistance and length
