In electromagnetic induction, the generated electricity is actually a voltage called

Assessment: JAMB UTME - Physics - 2025 Subject: Physics

Question 1 Report

In electromagnetic induction, the generated electricity is actually a voltage called 

Answer Details

Electromagnetic induction is described by Faraday's law: whenever the magnetic flux linking a conductor changes, a voltage is set up across the conductor. That voltage is called an induced e.m.f. (electromotive force), and its size is given by \[\varepsilon = -N\frac{\Delta\Phi}{\Delta t}\] where \(N\) is the number of turns and \(\Delta\Phi/\Delta t\) is the rate of change of magnetic flux. The minus sign is Lenz's law: the induced e.m.f. acts in the direction that opposes the change producing it.

The key distinction the question is testing is that induction produces a voltage, not a current, as its primary effect. A current only flows if that e.m.f. is connected to a complete circuit. This is why the e.m.f. still exists across the ends of a rod moved through a field even when the ends are not joined, and it is why a generator is rated by its e.m.f.

An eddy current is a circulating current, not a voltage; it is one of the consequences of induction inside a solid block of metal, and it is measured in amperes. Watts measure power, so that quantity cannot be a voltage at all. "Inductor voltage" is not a standard term in this topic; the recognised name for the quantity produced by a changing flux is the induced e.m.f. When a question names a unit or a quantity, check the dimensions first: only a quantity measured in volts can answer "a voltage called ...".

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