Transcript The Emf Induced Across A Moving Straight Conductor

The Emf Induced Across A
Moving Straight Conductor
The Straight Conductor
• The straight conductor can be thought of
as a a single turn coil stretched out
The emf generated by a single turn coil is:
Where n=1
Remembering
N

t


t
  BA
A stationary straight conductor does not enclose any
area but as it moves it sweeps out an area each second
A=l x x
Length l
 Blx


t
t
Distance moved perpendicular to the field (x)
  BA
  Blx
 Blx


t
t
In a uniform field B does not change and the length of
the conductor stays the same so we can write

x

 Bl ( )
t
t
  Blv
Where B is the flux
density
l is the length of the
conductor
perpindicular to the
field
v is its velocity
Example 1
• An aeroplane with wingspan 20.5m travels
south to north at 310ms-1 a region where
the vertical component of the Earth
magnetic field is 3.0 x 10-5T.
What is the emf generated between the
wingtips?
Example 2
• A patient is pushed into an 3.2T MRI
scanner at 1ms-1. The patient has a 5cm
tungsten pin through the bone of one leg
at 900 to the field lines during this process.
• What is the emf generated between the
ends of the pin?
• What would happen if the pin was made of
steel?
Example 3
• A 2m scaffolding pole falls from a tall building. It
falls horizontally pointing East to West for 2
seconds.
• What is the average velocity of the falling pole?
• What is the average emf generated between the
ends of the pole as it falls.
(Horizontal component of the Earth field 5.4 x 10-5T,
Vertical Component of the Earth field 3.4 x 10-4 T)