Michael Faraday

Physicist and chemist — Michael Faraday (London 1791 – Hampton Court 1867) was a British physicist and chemist, among the greatest experimentalists in history. Of extremely humble origins and largely self-taught, he began as an apprentice bookbinder and became an assistant to Humphry Davy at the Royal Institution. In 1831 he discovered electromagnetic induction, that is, the fact that a changing magnetic field generates an electric current: this is the principle behind dynamos, alternators and transformers, and hence all modern electricity generation. He formulated the laws of electrolysis, introduced the revolutionary concept of ‘lines of force’ and of field, which would inspire Maxwell, and discovered the rotation of the plane of polarisation of light in a magnetic field (the Faraday effect). Although he lacked mathematical training, his intuitive physical vision changed the way electromagnetism is thought about forever.

Fun fact

He turned down a baronetcy and burial in Westminster Abbey, preferring to remain ‘simply Mr. Faraday’, and on religious grounds refused to help produce chemical weapons during the Crimean War.

Theories and contributions

• Law of electromagnetic induction — The induced electromotive force equals the negative rate of change of magnetic flux: $\varepsilon = -\dfrac{d\Phi_B}{dt}$.
• Laws of electrolysis — The mass deposited at an electrode is proportional to the charge passed: $m = \dfrac{Q}{F}\cdot\dfrac{M}{z}$.
• Concept of field and lines of force — Electric and magnetic interactions described by means of a field that permeates space, rather than as action at a distance.
• Faraday effect — Rotation of the plane of polarisation of light passing through a medium immersed in a magnetic field: $\beta = V\,B\,d$.

Present in chapters

09 13 14 15 17 18 19 Z

Linked atoms

31 linked atoms.

09 Teoria cinetica dei gas

• Atoms: from philosophical hypothesis to experimental evidence

13 Forza di Coulomb ed elettrostatica

• From the torsion balance to Franklin’s lightning

14 Campo elettrico e potenziale

• Conductors in electrostatic equilibrium
• What is the electric field?
• Field lines: the five rules
• Counting lines: the field from density
• Two ways to calculate the field
• Field of a spherical shell

15 Circuiti elettrici

• The electric double layer

17 Il campo magnetico

• The electric motor
• Back-EMF and energy balance

18 Induzione elettromagnetica

• Magnetic flux
• Faraday’s resolution
• Circulation of E and the Faraday-Neumann-Lenz law
• The fictitious generator
• A roadmap for solving induction problems
• Lenz’s law as an independent principle
• Lenz’s minus sign
• Voltage across an inductor
• Self-induction and inductance
• The alternator and sinusoidal EMF
• When the electric field stops being conservative

19 Le equazioni di Maxwell e le onde elettromagnetiche

• The four equations (first, incomplete version)
• Displacement current
• Maxwell’s four equations
• Speed of electromagnetic waves
• The transformer
• Maxwell and unification: when c emerges from the equations

Z Appendice — Maturità

• Ministerial syllabus and book map
• Rod in a magnetic field: induction, dynamics and energy
• Key formulae — Electromagnetism