alleryStart learning →A bar magnet is held completely still inside a coil that is connected to a sensitive meter. What emf is induced in the coil?
AA steady emf
BNone at all
CA growing emf
DA large emf
Answer & Solution
Correct answer: B. None at all
1. An emf is induced only when the magnetic flux through the loop is changing.
2. A magnet held stationary keeps the field through the coil constant.
3. With no change in flux, the rate of change of flux is zero.
4. Faraday found that a voltage was generated only while the magnet was moving.
5. Holding the magnet still therefore induces no emf at all, however strong the magnet is.
6. Choosing a steady emf confuses a steady field with a changing one, which is the trap here.
_Source: Siyavula Physical Sciences Grade 11 (Everything Science, CC BY 4.0), Chapter 10: Electromagnetism_
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