Studied by 6 people
2 types of electricity
static electricity
current electricity
hazards of mains electricity
damaged insulation
overheating of cables
damp conditions
safety features built into domestic appliances
double insulation
earthing
fuses
circuit breakers
power
the rate of energy transfer or the amount of energy transferred per second
what is power dependent on
voltage and current
relationship between power, current and voltage
power = current x voltage
unit of power
watts
fuse
a safety device that cuts off the flow of electricity to an appliance if the current becomes too large
what do the ratings on a fuse tell us
how much current it can withstand
what does exceeding the current rating on a fuse cause
the fuse blows
should the fuse have a current rating higher than the current needed
yes
what will a low fuse current rating do
it will break the circuit even when an acceptable current is flowing through
what will a too high fuse current rating do
it will not be breaking the circuit in enough time before damage occurs
insulation
wires are covered with an insulating material as the conducting part of the wire is usually made of a metal that poses a risk of electrocution
double insulation
appliances with two layers of insulation
two layers of insulation in double insulated wires
insulation around the wires
a non-metallic cased
do double insulated appliances require an earth wire
no because the earth wire can't touch the metal casing
earthing
many electrical appliances have metal cases which poses a potential safety hazard if the live wire comes into contact with the case risking electrocution
how does the earth wire protects the user
the earth wire provides a low resistance path to the earth causing a surge of current causing the fuse to melt and break which cuts off electricity supply to the appliance
circuit breaker
an electromagnet switch that breaks the circuit if the current exceedds a certain value h
how does a circuit breaker work
it quickly shuts off electricity to the whole house
how is a circuit breaker better than a fuse
it doesn't melt and break and works much faster
DC
direct current
how does DC current travel
in one direction only
does a DC power supply have a fixed terminal
yes
AC
alternating current
how does AC current travel
it constantly changes direction
does an AC power supply have a fixed terminal
it has 2 identical terminals that switch between positive and negative
frequency of an alternating current
number of times the current changes direction back and forth each second
where is DC current produced/used
cells and batteries
where is AC current produced/used
electrical generators
when is work done
when charge flows through a circuit
relationship between work done and energy transferred
work done = energy transferred
relationship between energy transferred, current, voltage and time
energy transferred = current × voltage × time
why does temperature increase when electricity passes through a component
it's turned into heat
what is energy a transfer of
collisions between electrons flowing in the conductor and lattice of atoms within the metal conductor
current
flow of electrons
atomic configuration of metals
lattice of metals
what happens to electrons as they flow through metals
they collide with ions which resist the flow of electronsh
how does metal heat up
electrons collide and lose energy by giving it to ions which vibrate more
which appliances can the heating effect be utilised in
heaters, ovens, hobs, toasters, kettles
Note 
Flashcard (22)