During the 1820s Faraday sought to discover how to
make electricity from magnetism. He achieved success
with the device pictured above on 29 August 1831.
When he passed an electric current through one coil
he induced an electric current in the other coil, which
flowed for a very brief period of time.
When Michael Faraday made his
discovery of electromagnetic induction in
1831, he hypothesized that a changing
magnetic field is necessary to induce a
current in a nearby circuit. To test his
hypothesis he made a coil by wrapping a
paper cylinder with wire. He connected the
coil to a galvanometer, and then moved a
magnet back and forth inside the cylinder.
During the 1820s Faraday sought to discover how to
make electricity from magnetism. He achieved success
with the device pictured above on 29 August 1831. It's
made from everyday materials such as wire made for
bonnets, although the iron ring seems to have been
specially made.
Faraday’s magnetic induction experiment.
Ampere's law applied to an infinitely-long wire
predicts a magnetic field of strength B=m0I/(2pr) a
radial distance r from the wire. The field B is
tangential to a circle of radius r centered on the
wire.
We therefore have (B/I)=(m0/2p)(1/r). B/I is
proportional to 1/r, and when plotted versus 1/r will
yield a straight line with slope (m0/2p).
Consider the magnetic field around an infinitely long wire due to a current I flowing through the wire.
But B has the same value a distance a away from
the rod, hence
For the simple example, only one current linking the closed path C, therefore N = 1
(e
erial
ed
teri
ile
Loo
ismf)
by
al
we
kin
and
iron
so
is
can
g a
is
but
me
me
dev
at
use
ther
ba
asu
2. Biotelo
the
d
e
sic
re
Savart
p
infi
in
are
cur
of
Law an
nit
ma
othe
re
it's
It is
ana
e
gne
r
nt
ma
possible
lyti
wir
tic
elem
co
gne
to
cal
e
circ
ents
nfi
tic
determin
sol
aga
uits
such
gu
'str
e the
uti
in
to
as
rat
eng
magneti
on
we
det
coba
ion
th'.
c field
for
can
er
lt
s
Ma
generate
the
app
mi
and
usi
gne
d by a
axi
ly
ne
nick
ng
tisa
current
al
Am
the
el,
thi
tio
element
fiel
per
flux
as
s
n
using
d,
e's
den
well
la
can
the Biotit's
La
siti
as
w.
be
Savart
not
w
es
num
Co
inh
Law.
pos
as
in
erou
nsi
ere
sibl
foll
the
s
der
nt
Eqn
e
Fig
s
ow
8.2
var
8.1
alloy
an
in
to
s:
s iou
infi
the
do
s
The
like
nit
ma
this
at the general electromagnetic
principles which are widely employed in engineering. This is a very short introduction
to a complex subject. Yo
circ
tor
silic
If
ely
teri
for
and Forces
uit
us
on
the
lon
al,
the
at the case of the
pat
has
steel
relcoilgun it will be beneficial to briefly examine the fundamentals of electromagnetic fields and
g forces. Whenever there is char
suc
fiel
hs.
.a
uct
wir
h
d
Mm
me
Each
an
e
as
in
fin
an
isa
mat
ce
car
gen
me
rad
erial
ca
ryieach system has different unit
per
there are three systems of units in popular use, namely the Sommerfield, Kennely and Gaussian systems. Since
era
asu
ius
has
n
ng
ma
l.
red
aof
be
a r
ne
In
in
and
parti
det
cur
nt
ord
am
a
cular
er
re
ma
er
per
cro
prop
mi
nt
gne
to
esserty
ne
ti. or
fin
tur
sec
whic
d
We
it
d
ns
htio
the
ca
can
the
or
nal
mak
n
n
be
fiel
jus
are
es
we
us
gen
d it
tera
a
suita
ca
e
at
Magnetisation
n
System
of Units
-1
weber
Quantity
tesla
Am
Unit
M
m
H
B
I- (T)
(W)
Maxwell's
Equations
M
a
x
w
el
l'
s
e
q
u
at
io
n
s
c
o
n
Faraday's Law of Induction
The line integral of the electric field around a closed loop is equal to the
negative of the rate of change of the magnetic flux through the area enclosed
by the loop. This line integral is equal to the generated voltage or emf in the
loop, so Faraday's law is the basis for electric generators. It also forms the
basis for inductors and transformers.
Application to voltage generation in a coil
Gauss' law, electricity Gauss' law, magnetism Faraday's law Ampere's law
Maxwell's Equations
Index
Maxwell's equations concepts HyperPhysics***** Electricity and Magnetism
R NaveGo Back
Ampere's Law
In the case of static electric field, the line integral of the
magnetic field around a closed loop is proportional to the
electric current flowing through the loop. This is useful for
the calculation of magnetic field for simple geometries.
Gauss' law, electricity Gauss' law, magnetism Faraday's law
Ampere's law
Apply to charge conservation
Maxwell's Equations
Figure 6: Current i charging a capacitor as an
illustration of Maxwell’s displacement current (see
text).