EMI - Electromagnetic Induction

Electromagnetic Induction

Introduction

In our previous unit, we learned the important concept that an electric current can produce a magnetic field. After this discovery, the next question asked by scientists was "Can a magnetic field produce an electrical current?" An Englishman named Michael Faraday discovered that it was, indeed, possible to produce electricity from magnetic fields.

Faraday's experiment involved creating a magnetic field inside a coil of wire. The presence of the magnetic field alone was not enough to create electricity. However, changing the magnetic field through the wire coil induced a current, as measured on an ammeter connected to the loop. The main takeaway is that changing the magnetic field through a coil of wire induces an emf. This electromagnetic induction is at the heart of our electrical energy production today.

Moving a bar magnet into and out of a solenoid is one way to produce this induced emf. In the following video you will see this basic process in action. Remember that an ammeter is used to measure current. Whether the induced current is measured as positive or negative will show the direction of the current through the loop. While watching the video note the following:

1. The pole of the magnetic being inserted into the solenoid and the resulting current. 
2. The resulting current when the same magnet is removed from the solenoid.
3. The current reading when the magnet is stationary in the solenoid.

What you can see is that how the magnet is inserted (ex. north pole first) determines the direction of the current. When the magnet is removed, the current flows in the opposite direction. As it turns out, theres more to the relationship between the changing magnetic field and the induced emf. In the next unit we will delve deeper into the relationship as determined by Faraday.

As science and engineering have taught us, there's a close relationship between the theoretical and the practical. As we learned in the previous unit the theoretical understanding that an electric current can produce a magnetic field led to the development of the electric motor. Likewise, the theoretical understanding of electromagnetic induction has led to you being able to take this course (among many other amazing things). We will cover some of the most practical applications in the final lesson of this module. In the mean time, watch this video by Veritasium that talks about Faraday's discovery and shows a novel application, a levitating chandelier.

VIDEOS SOURCED FROM PUBLIC DOMAIN