Practice physics class test — Year 5: Maxwell and electromagnetic waves.
15 questions drawn at random from a bank of 25, on the block of the programme your teacher is finishing: every attempt is a different test. No penalty for wrong answers, so answer even if you are not sure. At the end you receive by email the correct answer to every question and your weak topics — with an account you see them straight away here on the page. The step-by-step solution unlocks with your first lesson.
A class test is the written test an Italian high-school class sits after each block of the programme; this practice version is multiple choice.
Test in ItalianThe questions of this simulator are in Italian, as in the real exam.
Programme covered by the test
- Maxwell’s four equations and what they mean
- Gauss’s theorem for the electric field and for the magnetic one
- Induced electric field and nonzero circulation
- Displacement current and the Ampere-Maxwell theorem
- Structure of a plane electromagnetic wave
- Speed of light in a vacuum and in media, the relation E = cB
- The electromagnetic spectrum and orders of magnitude
- Polarisation and Malus’s law
Two worked examples from the test
Quale delle quattro equazioni di Maxwell esprime il fatto che non esistono monopoli magnetici?
Solution
Il teorema di Gauss per il campo magnetico si scrive
Significa che tutte le linee di campo che entrano in una superficie chiusa ne escono: non esiste un punto da cui il campo magnetico «nasce» o in cui «muore», cioè non esiste una carica magnetica isolata.
È la differenza strutturale con il campo elettrico, dove il flusso vale e può quindi essere diverso da zero: le cariche elettriche isolate esistono, i monopoli magnetici no.
Conseguenza pratica: le linee del campo magnetico sono sempre chiuse, e spezzando un magnete in due si ottengono due magneti completi, non un polo nord e un polo sud separati.
Passando dai campi statici a quelli variabili nel tempo, quali delle quattro equazioni di Maxwell cambiano forma?
Solution
I due teoremi di Gauss restano identici: il flusso di dipende sempre dalla carica interna, quello di è sempre nullo.
Cambiano invece le due leggi sulle circuitazioni:
- in elettrostatica la circuitazione di è nulla (campo conservativo); con un flusso magnetico variabile diventa cioè la legge di Faraday-Neumann-Lenz;
- il teorema di Ampère, valido con le sole correnti di conduzione, va completato con il termine di corrente di spostamento dovuto al flusso elettrico variabile.
È proprio questa coppia di modifiche a rendere possibile l'onda elettromagnetica: un campo genera l'altro anche in assenza di cariche e correnti.
In the online practice test you will find 13 more questions like these; the correct answer to every question arrives by email.
Prefer paper? Download the test as a PDF (15 questions, 4 pages · 86 KB, ready to print). You receive the solutions by email after taking it online.
Download the PDFWhat a physics test on Maxwell and e.m. waves looks like
The physical meaning of the four equations one by one, the displacement current and why Ampere’s law had to be corrected, the structure of a plane wave with E = cB, the electromagnetic spectrum with orders of magnitude and Malus’s law.
The mistake that costs the grade
Saying that Gauss’s theorem for magnetism gives zero flux “because there are no closed magnetic fields”: it gives zero because there are no monopoles, and the lines are closed. On the wave, swapping E and B in the relation E = cB and getting an enormous magnetic field.
How to use this practice test
Take it once cold, without revising and with the timer on: it is there to show you where you stand, not to look good. Then look at your weak topics, revise only those — usually two or three, not the whole chapter — and retake it after a few days. The 15 questions are drawn from a bank of 25, so the second attempt is not the same test and the scores are genuinely comparable.
Is the score not enough?
See which topics lost you the most marks, then read the electromagnetism you need for the maturità — or we look at your results together: the diagnostic is free.