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Paper 3
10. Practical Skills
RP11 - Magnetic Flux Linkage
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Cards (12)
What pieces of apparatus can be used to measure the induced emf inside a current carrying circular coil?
A
search coil connected to an oscilloscope
Why must an alternating current source be used in this experiment?
An
AC
source should be used so that the
magnetic flux
through the
search
coil is constantly
changing
How can an oscilloscope be used to measure the induced EMF?
When connected to the search coil, the oscilloscope will show the
waveform
of the
induced EMF
By turning the
time base off
, this will become a
vertical line
that gives the
peak
to
peak value
of the EMF
What preliminary experiment will need to be undertaken before carrying this experiment out?
A preliminary experiment will be needed to determine a suitable
voltage
and
frequency
for the
circular coil
The induced emf must be
large
enough to be easily measured using the
search coil
and
oscilloscope
What is magnetic flux?
Magnetic flux is equal to the
product
of the magnetic flux
density
and the
area
through which it passes
It can be thought of as the number of
field lines
passing through a given
area
Suggest how angle measurements could be taken in this experiment
A
circular protractor card
could be positioned under the
circular coil
and fixed in place with an
optical pin
This allows the angle between the
circular coil
and the
search coil
to be
measured
from the
same position
each time
In what orientation will the maximum induced EMF and flux linkage occur in the search coil?
The maximum induced emf and flux linkage will occur when the search coil is
perpendicular
to the
magnetic field lines
This is when the angle is equal to
0 degrees
Why might an ammeter be required when carrying out the preliminary experiment?
It is important to ensure that the
current
passing through the
coil
doesn't
exceed
the manufacturer's
guidelines
In which orientation should the induced EMF be at a minimum?
The induced EMF should be
zero
when the search coil is
parallel
to the magnetic field lines
This is when the angle is equal to
90
degrees
What is magnetic flux linkage?
Magnetic flux linkage is
equal
to the
magnetic flux
passing through a
coil
multiplied by the number of
turns
that
cut
this
flux
What is the unit of magnetic flux?
Webers
(
Wb
)
Gradient Derivation:
N = BANcos (x)
I = I_0cos(ωt)
+ B
= B_0cos(ωt)
N = BANcos(x) = B_0cos(ωt)ANcos(x)
E = ΔN /Δt = - B_0ANΔsin(ωt)cos(x)
E_0 = B_0ANω cos(x)
when
sin (ωt) = 1 or -1
Where:
E_0 = y
B_0ANω = x
cos(x) = m