If a substance is positively or
negatively charged, it tries
to become neutral again by
receiving or losing electrons.
It tries to get
back to its natural
state, doesn't it?
By the way, objects can
be conductors, through
which electricity easily
flows (like metal)...
...insulators, through
which electricity has
diiculty flowing (like
gla or ruer)...
...and
semiconductors,
which are
midway betwn
conductors and
insulators.
Hm.
If there is an insulator betwn
a positive and a negative charge,
the electrons caot move.
Because the
electricity has
diiculty flowing,
right?
Current and Electrical Discharge
Insulator
30 Chapter 1 What Is Electricity?
If objects having a
charge are coected
by a conductor like a
coer wire...
...the negative electrons
move to the positive side.
Then the positives and negatives
unite to cancel each other
out, and the CHARGED state no
longer exists.
This phenomenon is
caed electrical
discharge.
Hm.
Electrical discharge
also ours in the air
or in a vacm.
A discharge
caneven our
inthe air?
Cuent and Electrical Discharge 31
twang!
This is what lightning is!
Lightning ours when tiny
water droplets in clouds
rub against each other, and
the static electricity that
was produced discharges
to the ground.
Then an
enormous
discharge
ours!
Since air is an
insulator, a
discharge does
not our easily.
When a large amount
ofcharge builds up,
andthere is a
dierence in potential
betwn the positive
andnegative charges...
or, in other words,
whenthe voltage
becomes veryhigh...
The insulation of the
air suenly breaks
down, and an electrical
discharge ours.
The breakdown
of the insulation
creates awesome
power, right?
It does!
But it haens
in an instant.
Hail and ice particles in
cumulonimbus clouds
coide with each other,
and electric charge
aumulates.
An electrical discharge
ours, either within the
cloud itself or in the
form of lightning to
the ground.
32 Chapter 1 What Is Electricity?
The discharge
of lightning is
instantaneous. But when
we have a continuous
flow of electrons, we
have cuent.
In other words,
when electrons are
continuously flowing,
electricity is flowing.
But one thing we
nd to be careful
about here is that
the direction of the
cuent is oosite
tothe direction
of the flow of
electrons.
Huh?
When electricity was sti
not we understd, it
was thought that the flow
of positive charge was in
the same direction as the
cuent.
But later,
after it was known
that electrons have
a negative charge, it
turned out that the
direction in which
the electrons move
is oosite to the
direction of the
cuent.
I s.
Direction of cuent?
Direction of cuent
Direction of electrons
Cuent and Electrical Discharge 33

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