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Multiple Choice

State Faraday's law of induction in words.

A changing magnetic flux through a loop induces a voltage in the loop. The strength of that induced emf is tied to how quickly the flux changes, and the negative sign (Lenz’s law) tells us the induced emf acts to oppose the change in flux. In words, the emf equals minus the time rate of change of the magnetic flux: ε = - dΦ/dt, where Φ is the magnetic flux through the loop (Φ = ∫ B · dA). This means changing the magnetic field, the loop’s size, or its orientation alters Φ and creates an emf. The other statements misstate this relationship: the emf is not simply the flux value itself, and while changing magnetic fields can generate electric fields, the defining relation for emf in a circuit is governed by the rate of change of magnetic flux, with the minus sign enforcing opposition to the change.

A changing magnetic flux through a loop induces a voltage in the loop. The strength of that induced emf is tied to how quickly the flux changes, and the negative sign (Lenz’s law) tells us the induced emf acts to oppose the change in flux. In words, the emf equals minus the time rate of change of the magnetic flux: ε = - dΦ/dt, where Φ is the magnetic flux through the loop (Φ = ∫ B · dA). This means changing the magnetic field, the loop’s size, or its orientation alters Φ and creates an emf. The other statements misstate this relationship: the emf is not simply the flux value itself, and while changing magnetic fields can generate electric fields, the defining relation for emf in a circuit is governed by the rate of change of magnetic flux, with the minus sign enforcing opposition to the change.