IB Physics HL topic guide

Fields

Fields is a core part of IB Physics HL. This guide connects the syllabus ideas behind Gravitational Fields and Forces, Orbital Motion, Electric Fields and Coulomb's Law, Electric Potential and Energy, Magnetic Force and Fields and 2 more units, shows how they appear in worked problems, and points you to the formulas and full lessons needed for exam revision.

What you will learn

Fields syllabus outline

The units below follow the structure used in the full Study to Learn course. Use the outline to identify exactly which idea needs attention, then work through the public example before continuing to the complete lesson path.

D.1

Gravitational Fields and Forces

Newton's Law of Gravitation and Field Strength · Gravitational Potential Energy and Escape Velocity

D.2

Orbital Motion

Orbital Mechanics · Geostationary Orbits and Satellite Applications

D.3

Electric Fields and Coulomb's Law

Coulomb's Law and Electric Fields · Uniform Electric Fields and Parallel Plates

D.4

Electric Potential and Energy

Electric Potential and Potential Energy · Motion of Charges in Electric Fields

D.5

Magnetic Force and Fields

Magnetic Force on Moving Charges · Circular Motion in Magnetic Fields

D.6

Motors and Hall Effect

DC Electric Motor · Hall Effect

D.7

Electromagnetic Induction

Faraday's and Lenz's Laws · Inductance and AC Circuits

Free worked preview

Faraday's and Lenz's Laws

This complete preview comes from the Electromagnetic Induction unit. It introduces the core language, shows the method in context, and gives you a real example of the lesson quality before you create an account.

Electromagnetic Induction

If a current creates a magnetic field (D.5), can a magnetic field create a current? Faraday's answer — only if the field is changing — is the principle behind every grid generator, every transformer, and every induction hob. Lenz's law, encoded in the minus sign of ε=−dΦ/dt\varepsilon = -d\Phi/dt, enforces energy conservation: the induced current always opposes the change that produced it.

A changing magnetic flux through a circuit induces an EMF:

Φ=BAcos⁡θ\Phi = BA\cos\theta
ε=−dΦdt=−NΔΦΔt(Faraday’s Law)\varepsilon = -\frac{d\Phi}{dt} = -N\frac{\Delta\Phi}{\Delta t} \qquad (\text{Faraday's Law})
Lenz's LawThe direction of the induced current is such that it opposes the change in flux that caused it. (The minus sign in Faraday's Law encodes this.)

AC Generator

A coil of N turns, area A rotating at angular frequency ω in field B:

Φ=BAcos⁡(ωt)  ⟹  ε=−NdΦdt=NBAωsin⁡(ωt)\Phi = BA\cos(\omega t) \implies \varepsilon = -N\frac{d\Phi}{dt} = NBA\omega\sin(\omega t)

Peak EMF: ε0=NBAω\varepsilon_0 = NBA\omega

Transformers

VsVp=NsNp(ideal: VpIp=VsIs)\frac{V_s}{V_p} = \frac{N_s}{N_p} \qquad (\text{ideal: } V_pI_p = V_sI_s)
Worked Example — Generator EMF A coil of 200 turns and area 0.050 m² rotates at 50 rad s⁻¹ in a 0.30 T magnetic field. Find the peak EMF generated.

ε₀ = NBAω = 200 × 0.30 × 0.050 × 50 = 150 V

Use the formulas

Keep the data booklet beside you

Revision becomes faster when you practise locating the right equation and understand what every variable means. The full reference is public and searchable on any device.

Open IB Physics HL Data Booklet →

Reviewed by the Study to Learn editorial team · Updated 2026-07-24