NCERT Book Class 12 Physics Chapter 6 Electromagnetic Induction

Physics

Chapter Six

ELECTROMAGNETIC
INDUCTION

6.1 INTRODUCTION
Electricity and magnetism were considered separate and unrelated
phenomena for a long time. In the early decades of the nineteenth century,
experiments on electric current by Oersted, Ampere and a few others
established the fact that electricity and magnetism are inter-related. They
found that moving electric charges produce magnetic fields. For example,
an electric current deflects a magnetic compass needle placed in its vicinity.
This naturally raises the questions like: Is the converse effect possible?
Can moving magnets produce electric currents? Does the nature permit
such a relation between electricity and magnetism? The answer is
resounding yes! The experiments of Michael Faraday in England and
Joseph Henry in USA, conducted around 1830, demonstrated
conclusively that electric currents were induced in closed coils when
subjected to changing magnetic fields. In this chapter, we will study the
phenomena associated with changing magnetic fields and understand
the underlying principles. The phenomenon in which electric current is
generated by varying magnetic fields is appropriately called
electromagnetic induction.
When Faraday first made public his discovery that relative motion
between a bar magnet and a wire loop produced a small current in the
latter, he was asked, “What is the use of it?” His reply was: “What is the
154 use of a new born baby?” The phenomenon of electromagnetic induction