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From YouTube: EM 2
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A
So
basically
electromagnet
induction
kind
of
gives
way
for
electrical
conductivity,
but
it's
a
very,
very
different
experiment
and
it's
one
as
I
said
that
you're
used
to
if
you
went
through
airport
security.
The
following
things
are
after
me:
we've
got
a
source
over
here
which
gives
a
time
varying
magnetic
needle
a.
B
A
And
we
have
a
lie:
detector
or
metal
detector.
Something
like
that.
15
that
I
didn't
show
yesterday
was
just
kind
of
interesting.
Is
that
the
physics
that
we
did
for
this
guy
doesn't
change
at
all?
We
can
just
scale
things
up
this
beautiful
thing
about
left.
So
here's
an
example
where
we
now
have
a
transmitter.
That's
mounted
on
a
clean
and
we're
looking
for
a
big
body
in
here
same
thing,
time,
very
good.
Magnetic
field
generates
collecting
field.
There's
ever
any
I'm
going
to
be,
there
could
get
currents.
A
Those
currents
give
rise
depending
same
process,
small
scale
a
scale,
so
this
is
kind
of
how
we
we
can
be
sort
of
set
things
up
with
the
basic
experiments,
and
that
motivation,
especially
for
airport,
is
that
we
have
these
really
large
areas
that
we
want
to
want
to
cover,
and
so
we're
going
to
fly
the
plane
up
in
the
air.
So.
A
So
the
physical
property
was
the
electrical
conductivity
which
we
said
basic
principles,
we're
gonna
step
through
this
thing
right
now.
So
the
very
first
thing
is
that
we're
gonna
have
our
kind
of
signature
experiment
here,
helicopter
it's
going
to
be
toy
bird.
That
has
got
a
transmitter
on
it
positively.
A
A
A
A
When
we
were
talking
at
the
beginning
of
this
course
about
magnets,
we
talked
about
the
strength
of
the
magnet
when
we
convert
that
to
this
friend
newish
the
strength
of
the
magnetic
an
iterative
magnetic
moment.
M
is
the
product
of
the
current
as
in
the
loop
type
C
area,
so
the
bigger
the
area
of
the
loop
stronger,
the
the
current
bigger
the
magnetic
moment
is
just
think
about,
like
okay
I've
got
a
bigger
magnet.
So
that's
that's
that
relationship
between
magnetic
moment
and
I
know.
This
is
the
same.
A
A
These
things
just
think
about
these
things
that
these
words,
so
this
is
time
rate
of
change
of
yes,
and
that
gives
rise
to
an
electric
field.
Every
clip,
okay,
there's
an
important
thing
here
and
that's
a
minus
sign.
You're
gonna
see
that
coming
into
things
a
lot.
Basically,
it's
the
system
that
the
earth,
if
these
currents
are
going
to
be
created,
they're
going
to
go
in
a
particular
direction.
A
A
So
that's
an
important
part.
So
we
can
easily
see
that
okay,
a
time-varying
magnetic
field,
is
going
to
give
circular
electric
fields.
Okay,
so
I'm
gonna
have
circular
currents
well,
which
way
are
they
going
on
well
they're,
going
to
go
in
such
a
way
that
they're
going
to
oppose
any
change,
so
the
magnetic
flux
is
increasing.
A
B
A
See
that
here
and
you're
probably
familiar
with
this-
you
probably
did
this
in
first
year.
So
this
is
what
we've
got.
We
got
a
coil
of
wire
and
it's
all
going
to
be
hooked
up
to
a
circuit,
so
we
could
measure
the
voltage
and
there's
a
light
bulb.
So
we
ever
get
any
current
that
goes
through
here.
There's
going
to
be
a
link
so
right
now
I'm,
not
a
magnet
city.
Just
like
this
I
got
North
Pole,
which
way
the
field
lines
go.
A
A
Just
plot
things
out
a
little
bit
more
in
detail,
so
here's
now
the
magnetic
field
lines
they're
going
like
this
and
I'm
going
to
introduce
something
called
the
magnetic
flux,
so
be,
if
you
remember
notice
what
we're
talking
about
it.
Ee
was
magnetic
flux,
density,
so
flux
Jessie
that
was
ever
per
meter
squared
if
I
take
a
lude
wire
if
I
put
a
magnetic
field
through
that.
B
A
Well,
that's
hand
side
of
this
equation,
which
is
which
is
Faraday's
law.
If,
if
I
write
the
whole
thing,
this
whole
thing
is
as
a
circuit
diagram
I've
got
a
resistance
here
with
my
light,
bulb
I've
got
a
coil,
so
it's
got
a
self-indulgence
good
and
the
Faraday's
law
says
that
the
voltage
that's
going
to
be
a
new
student
in
here
is
equal
to
minus
D,
Phi
B,
so
minus
the
time
rate
of
change.
A
So
right
now,
but
look
at
this
today,
nothing's
happening
so
there's
no
time
rate
of
change,
there's
a
box,
but
no
time
range.
So
everything
looks
like
that.
However,
if
I
take
this
magnet
and
I
push
it
in
okay,
so
not
going
to
push
the
magnet
in
so
the
strength
of
Magnus
gonna
get
a
high
strength.
Is
gonna
come
closer
to
coil,
so
I
bring
the
increasing
the
flocks.
A
A
My
flux
is
increasing,
so
deep,
I
ve
keep
increases
that
is
minus
sign
here.
So
I've
says
that
the
voltage
is
less
than
zero,
so
that
means
it's
going
in
okay.
So
that's
what
happening
I
take
my
coil
Irvine
doggy's,
the
quality
I
push
it
up,
cuz,
there's
time
varying
flux.
Okay,
the
current
opposes
it
and
now
I'm,
there's
current
in.
A
A
A
This
is
the
simplest
of
the
accent
we
keep
it
generated,
it's
a
coil
out,
so
there
is
a
primary
magnetic
field
or
the
primary
coil
that's
generated
by
this
guy.
Here,
sir,
it's
going
to
generate
field
and
ever
going
to
have
that
impinging
on
a
target
boost
that
has
got
a
particularly
distance
at
inductance,
and
then
we
can
see
what
the
currents
are
going
to
be
right.
So
just
to
this
again,
so
we've
got
we're
going
to
have
a
coil
up
here.
A
So
this
is
going
to
be
a
primary
and
then
we'll
have
say
a
letter
coil
down
here.
So
here's
going
to
be
our
targeting
and
if
we
change
the
current
in
here,
that's
going
to
change
the
magnetic
flux
that
goes
through
here
and
that
is
going
to
change
or
if
you
slit
current,
then
you're
going
to
be
able
to
experiment
with
this
I'm
not
going
to
thank
you
through
that
I'm
not
going
to
show
you
the
diagram
and
then
you
can
also
move
this
target.
A
At
this
point,
what
I
simply
want
to
do
was
to
take
you
through
the
following
steps.
So,
let's
suppose
in
our
primary
out
here,
we've
got
a
current.
Somehow
this
current
comes
here:
students
primary
magnetic
field,
it's
coming
vertically
down
and
if
our
primary
current
is
on
and
no
shirt
it
off
in
quickly.
So
this
is
the
primary
current
as
a
function
of
time.
A
A
A
B
A
A
So
that's
what
that's
what's
shown
up
here:
we've
got
different
kinds
of
conductors,
so
they're
different,
different
different
towels
if
tau
is
large
and
it
kind
of
slowly
top
small
okay.
So
let's
just
consider
we've
got
that
consolidated
now
in
the
time
to
me.
So
our
nose
is
a
coil.
Okay,
I
put
a
time-varying
magnetic
field
on
here
and
I'm.
Just
gonna,
stop
it
so
I
got
got
a
magnetic
field,
constant
I,
just
turn
it
off
the
moment.
I
turn
it
off.
There's
going
to
be
a
response.
A
A
Just
well
what
happens
if
I
do
something
a
bit
different
and
instead
of
having
the
current
that
looks
like
yes,
yes,
so
now
it's
gonna
be
our
blind
curve
right.
So
that
complicates
things
a
little
bit
because
now
yeah,
but
there's
always
a
time
varying
change
field.
Well,
so
I'm
going
to
have
to
somehow
keep
that
so
here's
what
your
second
app
is
and
it's
for
what's
called
a
harmonic.
So
that
means
just
a
science
book.
So
it
looks
like
that.
A
So,
let's
just
kind
of
parse
that
out
a
bit
and
you're
playing
with
this
app
this
afternoon
and
you're
going
to
be
looking
at
all
of
the
pieces
that
are
here
so
I'm
gonna,
try
to
explain
now
really
really
careful.
So,
let's
start
with
the
with
the
primary
field,
so
I
got
a
current
and
it's
just
the
awesome
indeed
correct.
So
it
looks
like
this,
so
it's
the
active,
the
fire-maker
cosine.
B
A
A
That
are
generated
in
response
to
that
time,
varying
magnetic
field,
and
the
question
is
like:
what
can
they
be?
They
can't
just
be
like
a
decaying
thing
that
we
saw
the
time
to
make
because
they
again
foxes
continue
to
change,
so
they
have
to
oscillate.
So
if
currents
inside
Samantha
are
oscillating,
you
know
it's
a
particular
frequency,
but
what
frequency
can
be?
The
only
frequency
that
it
could
be
is
the
same
one
as
as
what
the
input
current
is.
A
A
B
A
A
A
A
A
B
A
A
This
is
what
we
have
here,
so
I've
got.
A
primary
field
is
red.
Here's
our
primary
alright,
and
now
the
secondary
looks
like
this.
So
you
see
it's
got
a
different
altitude,
but
there's
also
fasion.
If
you
look
at
the
P
here,
look
keep
here,
they're
different,
okay,
so
there's
a
phase
shift
inside
that
phase
is
given
by
poets
I
like
to
and
then
there's
an
arc
of
Omega.
A
A
A
A
So
we
what
this
does.
Okay,
it's
sort
of
partition,
the
secondary
current
into
a
kind
of
in
phase
phase
ona
and
the
quite
key.
That's
important!
Is
this
alpha
here
only
get
out
on
mark
and
that's
called
the
abduction
number
we're
going
to
see
right.
So
this
is
the
induction
number
of
a
circuit
and
ending
upon
whether
that
induction
number
is
small
or
large.
We
get
different
kinds
of
partitioning.
If,
if
alpha
and
duxelle
number
is
really
small,
then
most
of
the
response
is
actually
in
the
other
things
part
if
the
induction
number
is
large.
A
A
This
is
an
important
plot
to
remember.
You
can
see
this
time
and
time
again
because
it
contains
so
much
information
and
it
helps
you
really
understand.
What's
going
on
I'm
going
to
show
you
I'm
going
to
give
you
a
case,
history
work
that
we
get
many
many
years
ago
on
the
expo
labs
after
Expo
87
mighty
low
before
your
time.
A
The
area
was
found
out
to
be
a
little
bit
polluted,
and
so
one
of
the
techniques
that
was
that
was
used
was
a
frequency
domain.
Vm
system
that
went
both
poles
of
the
regions
called
an
e
and
31,
and
that
instrument
collected
both
the
in
phase
and
the
other
phase
and
we're
actually
able
to
use
that
to
find
a
both
types.
Hydrocarbons
we're
going
to
hold
all
of
that
into
a
little
bit
of
this
week's
lab,
but
then
also
do
an
ex-lap.
A
A
A
A
A
A
A
Okay,
so
that
actually
is
going
to
be
how
the
whole
system
is
work.
We're
gonna
have
we're.
Gonna
have
two
coils
we're
gonna,
have
a
coil
for
transmitter,
okay
and
then
generate
some
currents
and
then
we're
going
to
measure
the
strength
of
those
by
measuring
the
voltage
in
another
cloud.
So
it's
like
it
recoiled.
A
So
here's
an
important
aspect
here
and
it's
all
called
coupling,
but
let's
take
let's
first
of
all
think
about
that
coil
system
that
we're
working
with
so
here's
your
transmitter,
the
magnetic
fields
in
that
transmitter.
This
looks
like
a
guy
who
looks
like
that
suppose.
I
have
a
coil,
that's
sitting
right
on
me
here
soon.
Mattoon
is
now
being
the
target
target
right,
so
Nautica
the
target
is
sitting
right
on.
There
lived
two
blocks
right:
it's
just
coming
smack
down,
so
I've
got
four
maximum
out
of
flux.
A
A
A
A
And
we
want
to
maximize
that
ball.
So
that's
what
we're
seeing
here
you've
got
examples
of
coupling.
So
here's
my
transmitter
here
is
my
target.
That's
perfect
coupling!
If
it's
sitting
over
here
I,
don't
have
anything
it's
like
coupling
and
the
city
someplace
else,
so
you'll
be
able
to
explore
that
also.
A
A
This
diagram
is
actually
more
general
than
that
because
now
we
could
imagine
that
this
guy
here,
okay
now
he's
the
currents
in
Samantha
I've
got
to
get
that
information
over
here
to
another
loop
I've
got
to
orient
that
problem.
So
there's
there's
two
levels
here.
So
this
is
the
initial
transmitter
and
here's
your
target.
Okay
and
then
the
next
thing
is
they'll
say
diagram
holes.
A
If
this,
if
I
thought
of
that
as
being
my
currency
in
my
target
loop
and
then
here
in
C,
my
receiver
I
still
have
that
same
kind
of
equations,
so
that
actually
allows
us
to
put
together
the
physics
on
a
slide
that
at
first
sight
what
in
fact
is
actually
really
understand.
Here's
how
we're
going
to
do
it.
So
our
general
idea
about
a
geophysical
experiment
for
electromagnetics
is
as
follows:
we
got
transmitter,
but
ever
teamed
up,
we've
got
a
conductor
in
here
that
we're
going
to
get
these
currents.
A
I
never
mentioned
this
word,
but
sometimes
those
are
called
eddy
currents
induced
currents.
Any
currents,
so
we
get
these
currents
and
reception.
Those
currents
give
rise
to
a
secondary
field
that
could
be
measured
after
receipt.
I
told
you
that
everything
depends
upon
coupling
and
here's
how
we
could
define
it.
So,
let's
place
these
three
guys
here
with
three
loops.
So
here's
our
transmitter
represent
our
target
body
by
another
loop
and
our
receiver
by
a
third.
A
B
A
We're
stuck
we're
just
kind
of
thinking
about
strengths,
of
things.
We're
gonna
have
to
know
how
this
move
of
this
couple
together
right.
So
we're
actually
going
to
use
that
as
like
an
geometric
factor,
it's
called
a
coupling
coefficient
evaluated
like
that,
but,
let's
just
think
about
m12
as
just
how
this
loop
couples
with
that
you
are
they
perpendicular
planar,
so
that
kind
of
tells
you
the
strength
of
the
inducing
fields
as
they're
getting
down
here
and
now
we
get
these
currents
that
are
going
in
here.
A
A
Now
that
could
be
compared
with
the
amplitude
of
this
direct
wave
here
primary
field,
which
is
the
coupling
between
this
and
that
that
simple.
So
these
terms
here,
you
can
understand
geometrically,
just
physically
understand
them.
There
just
have
to
do
with,
and
then
there's
all
this
stuff
over
here
that
involves
this
induction
number
and
there's
I
square
root.
Imaginary
number
of
think
you
guys
are
overly
how
many
people
do
you
have
to
work
with.
You
know
in
each
of
the
eye
or
because
TV
in
fact,.
A
A
A
A
So
now
we
gotta
do
one
more
thing:
see:
okay,
so
here's
here's,
the
scoop,
took
Department
a
lot.
So
let's
that's
first
of
all,
think
about
what's
great,
so
we've
got
a
transmitter
and
receiver
and
let's
suppose
that
they're
both
on
the
left
hand,
side.
Okay,
so
I've
got
now
a
magnetic
field.
That's
going
like
this
another
clue!
That's
the
primary
field!
Okay,
the
less
holes!
That's
changing
now,
just
as
we
talked
about
there's
going
to
be
an
induced
current
in
here,
okay,
there's
gonna
be
pretty
to
oppose
that.
A
A
A
It's
hitting
this
receiver
Luther
horizontally,
so
there's
no
flux.
That's
coming
through
here.
There's
no
signal!
So
that's
going
to
give
us
a
zero
cross.
If
I
do
one
more
steps
of
my
transmitters
on
the
left
and
right
now,
what
I
have
is
something
that
is
true,
so
lest
I
still
get
my
currents
into
that
direction
and
because
they're
going
to
be
opposite
signs
in
my
procedure,
I
can
plug
this
thing.
A
A
A
So
that's
that's
where
you're
going
to
be
the
last
thing
just
to
say
is
that
here's
your
response
curve,
so
what
we
showed
that
here
is
Joffrey.
Oh
that's,
just
just
John
when
you
actually
go
out
into
the
field,
you
might
be
in
position
something
like
this,
where
the
curves
panel
that
will
always
work
the
same.
That's
the
geometry
but
I
think
the
red
part
here
is
a
higher
altitude
yeah
and
that's
where
your
response
function
comes
back.