electromagnetic induction can a magnet produce electricity?
TRANSCRIPT
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Ele
ctro
magneti
c In
duct
ion
Can a magnet produce electricity?
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Mic
hael F
ara
day
An English scientist who was first to prove that a magnet can produce current.
A magnet can produce
electricity!
Duh!
Joseph Henry
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What conditions are necessary for a magnet to produce current?
Magnet must be moving or
Wire must be moving
Movement causes changing magnetic field
Changing magnetic field induces current
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Ele
ctro
magneti
c In
duct
ion
The phenomenon by which an emf or current induced in a conductor due to change in magnetic field.
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What factors affect the nature of emf or current produced?
Direction of motion In or out
Speed of motion Polarity of magnet
coming in
Number of turns
Area of coil
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Dir
ect
ion o
f M
oti
on
The direction of the current induced opposes the change producing it
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Speed o
f M
oti
on The faster the
movement is, the greater is the induced emf.
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Pola
rity
of
magnet
The induced current produces a magnetic field that opposes the one causing it.
Use RHR
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Num
ber
of
turn
s The more the number of turns, the greater the emf induced.
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Law
s of
EM
in
duct
ion Faraday’s Law
The induced emf across the conductor is equal to the rate at which magnetic flux is cut by the conductor.
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Magneti
c Fl
ux
Product of flux density (B) and the area (A), when flux is at right angles to the area.
Ø= BA
Unit: Weber, Wb
A weber is the flux when a unit tesla of magnetic flux density is at right angles to a unit area.
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Magneti
c Fl
ux
Linka
ge
Total flux cut by all turns of the coil
Ø= BAN
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So f
ar…
EMF = dØ /dt
For single coil EMF = BA/t
For many coils EMF = BAN/t
For a wire EMF = Blx/t
Where l is length of wire and x is distance traveled.
EMF = Blv Where v is the speed
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Lenz’
s La
wThe direction of any
induced current is such as to oppose the change that causes it.
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There
fore
EMF = - dØ /dt
For single coil EMF = - BA/t
For many coils EMF = - BAN/t
For a wire EMF = - Blx/t
Where l is length of wire and x is distance traveled.
EMF = - Blv Where v is the speed
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Exa
mple
1 A straight wire of length 0.2 m moves at a steady speed of 3 ms-1 at right angles to a magnetic field of flux density 0.1 T. What will be the emf induced across the ends of the wire?
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Exa
mple
2
A coil of wire having 2500 turns and of area 1 cm2 is placed between the poles of a magnet so that the magnetic flux passes perpendicularly through the coil. The flux density of the field is 0.5 T. The coil is pulled rapidly out of the field in a time of 0.1 s. What average emf is induced across the ends of the coil?
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Investigating Lenz’s Law
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Uses of EM Induction (Generator)
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Transfo
rmer
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Use
s of E
M
Inductio
n
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