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group 4
1.
Firdiana Sanjaya
4201414050
2.
Ana Alina
4201414095
Linking electricity and magnetism
Linking electricity and magnetism
From these observations, we conclude that
the loop detects that the magnet is moving relative
to it and we relate this detection to a change in
magnetic field. Thus, it seems that a relationship
exists between current and changing magnetic
field.
Linking electricity and magnetism
The conclution from all these observations is that a
changing magnetic field will produce a voltage in a
coil, causing a current to flow. To be completely
accurate, if the magnetic flux through a coil is
changed, a voltage will be produced. This voltage is
known as the induced emf.
Linking electricity and magnetism
The magnetic flux is a
measure
magnetic
of
the
field
number
lines
of
passing
through an area. If a loop of wire
with an area A is in a magnetic
field B, the magnetic flux is given
by:
Linking electricity and magnetism
If the flux changes, an emf will be induced. There
are therefore three ways an emf can be induced in
a loop:
• Change the magnetic field
• Change the area of the loop
• Change the angle between the field and the loop
Faraday's law of induction
• an emf can be induced in a coil if the
magnetic flux through the coil is changed.
It also makes a difference how fast the
change is; a quick change induces more
emf than a gradual change. This is
summarized in Faraday's law of induction.
The induced emf in a coil of N loops
produced by a change in flux in a certain
time interval is given by:
• Recalling that the flux through a loop of area A
given by
• Faraday’s law can be written
An example
• Consider a flat square coil with N = 5 loops. The coil is
20 cm on each side, and has a magnetic field of 0.3 T
passing through it. The plane of the coil is perpendicular
to the magnetic field: the field points out of the page.
(a) If nothing is changed, what is the induced emf?
There is only an induced emf when the magnetic flux changes, and while
the change is taking place. If nothing changes, the induced emf is zero.
(b) The magnetic field is increased uniformly from 0.3 T to 0.8 T in 1.0 seconds.
While the change is taking place, what is the induced emf in the coil?
Probably the most straight-forward way to approach this is to calculate the initial
and final magnetic flux through the coil.
The induced emf is then:
thanks
Any question?