ELECTRICITY / ELECTRONS
1/5
metal ion (+)
free electron (−)
no push: each electron jitters at random, so on average nothing flows
NET FLOW = 0
Metal
is
full
of
free
electrons
ELECTRICITY / DRIFT
2/5
voltage pushes electrons from − towards +
ELECTRONS PAST THIS LINE PER SECOND = CURRENT (A)
● ● ● ● ● ● ● ●
A
voltage
gives
them
a
push
ELECTRICITY / THE LOOP
3/5
+
−
battery
keeps the push
going (volts)
the bulb uses the flow
electrons flow out of −, round the loop, back into +
CURRENT IS THE SAME
AT EVERY POINT
Current
flows
round
a
closed
loop
ELECTRICITY / RESISTANCE
4/5
thick copper: an easy path
thin filament: high resistance
the same number of electrons must squeeze through, faster
they keep hitting the ions — that energy comes out as heat and light
POWER AS HEAT = I² × R
Resistance
turns
flow
into
heat
ELECTRICITY / SWITCH
5/5
+
−
switch
opens a gap
no closed loop, no current — anywhere
each electron drifts less than a millimetre a second,
but the push travels round the wire at a large fraction of light speed
Open
the
loop
and
it
stops
at
once
How
does
electricity
flow?