Question

How does the magnitude, sign, and rate of change of the magnetic flux, and the number of turns in the secondary affect the induced emf? In an experiment of Moving a permanent magnet AND an electromagnet in and out of a pickup coil and seeing the brightness or voltage.

Relating to Faraday's Law

Answer 1

First of all, a permanent magnet and an electromagnet behaves in the same way. The only difference is in the method of producing magnetic fields.in a permanent magnet magnetic field is produced by magnetic moment of moving charges while in an electromagnet magnetic field is produced using a current carrying coil.

Coming to the anwer of this question,faraday's law states that the EMF produced in the coil is equal to the rate of change of flux passing through the conductor.

Now let's see how the above mentioned quantities affect the EMF produced in this case:-

a. Magnitude of magnetic flux- magnetic flux is equal to (magnetic field) X (area). If the rate of insertion and taking out of the magnet is kept fixed, a larger magnetic field will cause a larger rate of change of flux does the EMF induced will also be larger.

b.sign- the sign of magnetic flux will only influence the direction of EMF induced. If you reverse the sign of magnetic field it will only result in a reversed polarity of the induced EMF.

c. Number of turns- if magnetic flux changes through one coil it will induce an EMF in that coil. If the flux changes through two coils it will induce EMF in both coils and so on if we keep on increasing the number of turns the EMF induced in each coil will be added up and the net induced EMF will increase.