The principle that states that if a conductor is static and the magnetic field around it is varying, an electromotive force (emf) will be induced is called “static induced emf.” Therefore, the correct answer is C: “static induced emf.”
Here’s a further explanation:
When a conductor is static (i.e., not in motion) and there is a changing magnetic field around it, Faraday’s law of electromagnetic induction states that an emf will be induced in the conductor. This phenomenon is known as static induced emf or stationary induced emf.
According to Faraday’s law, a time-varying magnetic field induces an electric field, which, in turn, creates a potential difference or emf across the conductor. This emf can drive an electric current in a closed circuit if there is a complete path for the current to flow.
It’s important to note that in the case of static induced emf, the conductor itself remains stationary, while the magnetic field around it is changing. This can occur, for example, when a magnetic field is varied by moving magnets or by changing the current in nearby conductors.
The induced emf in a static conductor is given by the equation:
emf = -dΦ/dt
where emf represents the electromotive force, dΦ/dt represents the rate of change of magnetic flux, and the negative sign indicates the direction of the induced emf according to Lenz’s law.
Therefore, the principle that describes the induction of emf in a static conductor in the presence of a varying magnetic field is called “static induced emf” (option C).