When a conducting rod moves at right angles to a constant magnetic field, the magnetic force causes opposite charges to appear at the end of the rod, giving rise to an induced emf. If the length of the rod is reduced by a factor of 4, for the induced emf to be the same, what should be done?Without changing the speed of the rod, increase the strength of the magnetic field by a factor of four.Without changing the magnetic field, increase the speed of the rod by a factor of four.Increase both the speed of the rod and the strength of the magnetic field by a factor of two.All of the 3 methods listed here may be used.