Download Hall Effect

Hall Effect
E and B
 Charged particles can be subject to both electric and
magnetic fields.
FM  qvB
FE  qE
FE  FM
qE  qvB
v
E
B
Deflected Current
 A wire with current has moving
l
I
q
q
t
FM
B
charges.
• Current due to electric field
• Subject to a force from
magnetism.
 The force can be related to the
current.
FM  qvBsin 
FM 
q
vt B sin 
t
FM  IlB sin 
• Charge times velocity
• Current time length
Charge Pileup
A
 Moving current in the magnetic
l
q
I
 nqAv
t
FE
q
FM
q
q
v
I
nqA
field will move carriers.
• Only carriers of current move
• Motion same for either sign
charge.
 The charges set up an electric
B
field.
• Opposes magnetic force
FE  qE
FM  qvB
E  vB 
IB
nqA
 This is called the Hall effect.
Cross Potential
A
V  Ew
l
E
I
w
q
q
 An electric field is created in
the conductor.
• Perpendicular to current and
magnetic field
q
 The electric field creates a
B
potential V.
• Based on width w
• Area is width times thickness x
V  Ew 
IB
nqx
Carrier Sign
A
V  Ew
l
E
I
w
q
q
q
B
 The Hall voltage depends on
the magnetic field, current and
the charge carrier properties.
• Number density n
• Charge q
 The sign of the potential
matches the sign of the charge
carriers.
IB
V  Ew 
nqx
• Negative for electrons
 Some conductors have
positive carriers.
Hall Probe
 The Hall effect can be used to
measure magnetic fields.
• Apply known current to known
material
• Measure Hall voltage
nqx
B
V
I
Integrity Design, Inc.
Blood Flow
 Similar to the Hall effect, the velocity of blood can be
measured by its ions.
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