Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

Theme D — Fields

D.4.2 Magnetic Flux — IB Physics HL Revision Notes & Topical Questions

5 min read 8 parts Lesson 36 of 39 1 quiz

📚 IB Physics HL Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read
Lesson summary

D.4.2 Magnetic Flux — IB PHYSICS HL notes: Define magnetic flux and flux linkage and use Φ = BA cos θ and NΦ.Definition — the product of the magnetic flux density and the cross-sectional area perpendicular to the fieldPerpendicular case — Φ = BAWhat the symbols mean: Φ = magnetic…

  • Symbol and unit
  • Component used
  • Rotating coil
  • Changing B
  • Changing A
  • Changing θ

Part 1 of 6Magnetic flux

Definition
  • Definition the product of the magnetic flux density and the cross-sectional area perpendicular to the field
Perpendicular case
  • Φ = BA
    What the symbols mean: Φ = magnetic flux (Wb) · B = magnetic flux density (T) · A = area at right angles to the field (m2)
Symbol and unit
  • Φ (phi) measured in webers (Wb)
Picture
  • Picture the number of field lines passing through a given area

Part 2 of 6Flux at an angle

Flux at an angle
Equation
  • Φ = BA cos θ
Angle
  • θ is between the field lines and the normal to the plane of the area
Maximum
  • Φ = BA when θ = 0° and the field is perpendicular to the plane
Zero
  • Φ = 0 when θ = 90° and the field is parallel to the plane
Component used
  • Component used the component of B perpendicular to the area
Rotation
  • Rotation the flux of a coil varies as it rotates in the field

Part 3 of 6Flux linkage

Definition
  • Definition the product of the magnetic flux and the number of turns of the coil
Equation
  • NΦ = BAN cos θ
Unit
  • Unit weber turns (Wb turns)
Use
  • Use it is commonly used for solenoids and coils of N turns
Rotating coil
  • Rotating coil the flux linkage is a maximum when the field lines are perpendicular to the plane

Part 4 of 6Ways to change flux linkage

Changing B
  • Changing B a varying flux density
Changing A
  • Changing A a changing cross-sectional area
Changing θ
  • Changing θ a change in the angle, as in a rotating coil
E.m.f.
  • E.m.f. an e.m.f. is induced when the flux linkage changes with time

Part 5 of 6Using the equations

Units
  • Units convert area from cm2 or mm2 to m2 and flux density to tesla
Shapes
  • Shapes areas such as the circle πr2 are in the data booklet
Graph
  • Graph the flux against angle follows a cosine curve

Part 6 of 6More from the specification

More from the specification
Magnetic flux linkage and energy
  • Magnetic flux linkage and energy changing magnetic flux linkage through inductive coils transfers mechanical work into stored magnetic field energy.
Magnetic flux definition
  • Magnetic flux (Phi) is the product of magnetic flux density and normal surface area: Phi = B A cos(theta), measured in webers (Wb = T m2.
Magnetic flux linkage in coils
  • For a coil of N turns, the total magnetic flux linkage is given by N Phi = N B A cos(theta).
Faraday-Lenz law of electromagnetic induction
  • An induced electromotive force is directly proportional to the time rate of change of magnetic flux linkage: E = -N (dPhi / dt).
Electromagnetic induction in conductors
  • Electromagnetic induction in conductors moving an electrical conductor through magnetic flux induces voltage that drives current around a closed circuit.
Induced voltage and cutting speed
  • Induced voltage and cutting speed faster relative speed between magnetic field lines and conductor coils produces higher induced alternating voltage output.
Lenz's law and current direction
  • Lenz's law and current direction induced current creates an opposing magnetic field,
    • producing voltmeter deflections that reverse direction upon withdrawal.
Mutual induction
  • Induction of an e.m.f. in one circuit by a change of current in a neighbouring circuit.
Potential difference
  • Work done by a unit charge passing through a component.
Alternating current
  • Current that continually reverses direction.
Closed circuit
  • Complete loop with a source in which current can flow
Constant speed
  • Speed that does not change.
Electromagnetic induction
  • Production of an e.m.f. by relative movement of a conductor and a magnetic field.
Current
  • Flow of electrons in a circuit.
Induction
  • Charging an object without touching it, giving it the opposite sign to the charged object.
Conductor
  • Material that allows current to flow.
Frequency
  • Revolutions per second, f = 1/T.
    What the symbols mean: T = period, the time for one complete wave (s) · f = frequency (Hz)
Voltmeter
  • Instrument that measures p.d., connected in parallel.
Primary
  • Input coil.
Secondary
  • Output coil.
Angular speed
  • Magnitude of the angular velocity.

Key terms

TermMeaning
Magnetic fluxThe product of the magnetic flux density and the area perpendicular to the field, in webers.
WeberThe unit of magnetic flux, equal to one tesla metre squared.
Flux linkageThe product of the flux through a coil and its number of turns.
NormalThe line perpendicular to the plane of the area.

Avoid these mistakes

1
Using the angle with the plane instead of the angle with the normal in cos θ.
2
Forgetting to multiply by N for flux linkage.
3
Leaving areas in cm2 instead of m2.
4
Saying flux is zero when the field is perpendicular to the plane — it is a maximum.

Last updated:

Transformer Golden Equations Physics Standard

Transformer Turns Ratio & Efficiency

Ratio: Vp / Vs = Np / Ns = Is / Ip

  • Step-up reduces grid thermal loss (P = I2R).
  • Laminated core prevents eddy currents.
\n