Electromotive force (EMF) is generated in a conductor when it moves through a magnetic field, and it is determined by several factors according to Faraday's law of electromagnetic induction. The factors that affect EMF include:
- The strength of the magnetic field
- The length of the wire in the field
- The velocity of the wire as it moves through the magnetic field.
However, the EMF does not depend on the number of electrons in the magnetic field. The number of electrons does not influence the generated EMF; instead, EMF is related to the rate of change of the magnetic flux and the motion of the conductor through the field.
Therefore, the answer to your question is:
the number of electrons in the magnetic field.