12.1.4
Magnetic Flux & Flux Linkage
Magnetic Flux Definitions
Magnetic Flux Definitions
Three terms that are closely related but different are magnetic flux, magnetic flux density and magnetic flux linkage.


Definitions
Definitions
- Magnetic flux is a measure of the number of field lines passing through a region of space.
- Magnetic flux density is a measure of the number of field lines passing through a region of space per unit cross-sectional area.
- Magnetic flux linkage is the product of the magnetic flux and the number of turns on a coil through which the field passes.


Different flux density
Different flux density
- The two loops in the diagram have the same flux but different flux densities since area Y is larger than area X.


Different flux
Different flux
- The two loops in the diagram have the same flux density but different flux since area Y is larger than area X.
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Different flux linkage
Different flux linkage
- The two loops in the diagram have the same flux and flux density, but as loop Y has twice the number of turns as loop X, the flux linkage in Y is twice that of loop X.
Magnetic Flux and Flux Linkage
Magnetic Flux and Flux Linkage
The formulae for magnetic flux and magnetic flux linkage are:


Magnetic flux, Φ
Magnetic flux, Φ
- The magnetic flux is the amount of magnetic field passing through a surface.
- The equation for magnetic flux is:
- Where is the flux, B is the field strength, A is the area and theta is the angle between the normal of the surface and the field.


Magnetic flux linkage, nΦ
Magnetic flux linkage, nΦ
- The magnetic flux linkage is the amount of field passing through a coil of wire. It is the flux 'linked' to a wire.
- The equation for the flux linkage is:
- Where N is the number of coils in the wire.
Magnetic Flux Linkage Experiment
Magnetic Flux Linkage Experiment
This experiment investigates how magnetic flux linkage varies with the angle between a search coil and the magnetic field direction. This is done using a search coil and an oscilloscope.


Apparatus
Apparatus
- Set up the apparatus as shown in the diagram.
- The search coil will experience a flux linkage as determined by the formula:
- .


Underlying theory
Underlying theory
- The magnetic field inside the coil will be uniform and running parallel to the length of the spring (across the page horizontally in the diagram).
- As the current is a.c., there will be a varying magnetic flux density through the search coil, and hence a varying flux linkage.


Underlying theory 2
Underlying theory 2
- This will induce an EMF in the search coil which is detected by the oscilloscope.
- The time base (time axis) of the oscilloscope is turned off, so that the a.c. induced gives a vertical line on the screen. The amplitude of this line (from the peak to the middle) gives the magnitude of the induced EMF.


Method
Method
- The search coil can now be rotated so that the angle between the plane of the coil and the magnetic field lines changes.
- By recording the amplitude of the induced EMF every 10 degrees, a graph of EMF induced against angle can be plotted, showing the relationship between the flux linkage and the angle between the normal to the plane of the coil and the magnetic field lines.
1Physical Quantities & Units
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3Kinematics
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13.2.17A-A* (AO3/4) - Nuclear Fusion
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1Physical Quantities & Units
2Measurement Techniques
3Kinematics
4Dynamics
4.1Momentum & Newton's Laws of Motion
4.2Non-Uniform Motion
4.3Linear Momentum & Conservation
4.4Force, Density & Pressure
4.4.1Fields
4.4.2Force in Uniform Fields
4.4.3Friction
4.4.4Buoyancy
4.4.5Terminal Speed
4.4.6End of Topic Test - Acceleration Due to Gravity
4.4.7Centre of Mass
4.4.8Forces & Equilibrium
4.4.9End of Topic Test - Scalars & Vectors
4.4.10Moments
4.4.11End of Topic Test - Moments & Centre of Mass
4.4.12Density
4.4.13Pressure
4.5Work, Energy & Power
5Gravitational Fields
5.1Gravitational Fields (A2 only)
6Deformation of Solids
7Thermal Physics
7.1Thermal Physics
7.1.1Temperature
7.1.2Measuring Temperature
7.1.3Ideal Gas Law
7.1.4Ideal Gases
7.1.5Boyle's Law & Charles' Law
7.1.6Molecular Kinetic Theory Model
7.1.7Molecular Kinetic Theory Model 2
7.1.8Thermal Energy Transfer
7.1.9Thermal Energy Transfer Experiments
7.1.10End of Topic Test - Thermal Energy & Ideal Gases
7.1.11First Law of Thermodynamics
8Oscillations
8.1Simple Harmonic Motion
8.2Waves
8.2.1Progressive Waves
8.2.2Intensity of Waves
8.2.3Wave Speed & Phase Difference
8.2.4Longitudinal & Transverse Waves
8.2.5End of Topic Test - Progressive Waves
8.2.6Electromagnetic Waves
8.2.7Doppler Effect
8.2.8Sound Waves
8.2.9Measuring Sound Waves
8.2.10End of Topic Test - Waves
8.2.11Ultrasound Imaging
8.2.12Ultrasound Imaging 2
9Communication
9.1Communication Channels
9.2Digital Communication
10Electric Fields
10.1Electric Fields
11Current Electricity
11.1Current Electricity
11.1.1Basics of Electricity
11.1.2Mean Drift Velocity
11.1.3Current-Voltage Characteristics
11.1.4End of Topic Test - Basics of Electricity
11.1.5Resistivity
11.1.6End of Topic Test - Resistivity & Superconductors
11.1.7Power and Conservation
11.1.8Microphones
11.1.9Components
11.1.10Relays
11.1.11Strain Gauges
12Magnetic Fields
12.1Magnetic Fields
13Modern Physics
13.1Quantum Physics
13.1.1The Photoelectric Effect
13.1.2The Photoelectric Effect Explanation
13.1.3End of Topic Test - The Photoelectric Effect
13.1.4Collisions of Electrons with Atoms
13.1.5Energy Levels & Photon Emission
13.1.6Wave-Particle Duality
13.1.7End of Topic Test - Absorption & Emission
13.1.8Band Theory
13.1.9Diagnostic X-Rays
13.1.10X-Ray Image Processing
13.1.11Absorption of X-Rays
13.1.12CT Scanners
13.2Nuclear Physics
13.2.1Rutherford Scattering
13.2.2Atomic Model
13.2.3Isotopes
13.2.4Stable & Unstable Nuclei
13.2.5A-A* (AO3/4) - Stable & Unstable Nuclei
13.2.6Alpha & Beta Radiation
13.2.7Gamma Radiation
13.2.8Particles, Antiparticles & Photons
13.2.9Quarks & Antiquarks
13.2.10Particle Interactions
13.2.11Radioactive Decay
13.2.12Half Life
13.2.13End of Topic Test - Radioactivity
13.2.14Nuclear Instability
13.2.15Mass & Energy
13.2.16Binding Energy
13.2.17A-A* (AO3/4) - Nuclear Fusion
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