19.0     INTRODUCTION

Electromagnetic Induction is a current produced because of voltage production (electromotive force) due to a changing magnetic field. This either happens when a conductor is placed in a moving magnetic field (when using an AC power source) or when a conductor is constantly moving in a stationary magnetic field.

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          19.1     FARADAY’S LAWS OF ELECTROMAGNETIC INDUCTION

• First Law: An emf is induced in a circuit when the magnetic field around it changes.
• Second Law: The induced emf is proportional to the rate of change of magnetic flux.

FACTORS AFFECTING INDUCED EMF

• Rate of change of magnetic flux.
• Number of turns in the coil.
• Strength of the magnetic field.

LENZ’S LAW – Lenz’s law states that the direction of the electric current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes changes in the initial magnetic field. It is named after physicist Heinrich Lenz, who formulated it in 1834.

Simply, Lenz law states that the direction of induced emf opposes the change in magnetic flux, illustrating conservation of energy.

          19.2     TRANSFORMER

Transformers are devices that transfer electrical energy between two or more circuits through electromagnetic induction.

• Voltage Ratio: (Voltage in primary coil / Voltage in secondary coil) = (Number of turns in primary coil / Number of turns in secondary coil). 
• Current Ratio: (Current in secondary coil / Current in primary coil) = (Number of turns in primary coil / Number if turns in secondary coil).
• Power Conservation: (Voltage across primary coil × Current in the primary coil) = (Voltage across secondary coil × Current in the secondary coil).

APPLICATION OF TRANSFORMERS 

• Voltage Regulation: Step up or step-down voltage for efficient power transmission.
• Power Distribution: Distribute electricity from power plants to consumers.
• Isolation: Provide electrical isolation for safety.
• Impedance Matching: Optimize power transfer in audio and RF applications.

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19.3     A.C. AND D.C. GENERATORS

• DC Generators: DC generators convert mechanical energy into electrical energy in the form of direct current.
• AC Generators (Alternators): AC generators convert mechanical energy into electrical energy in the form of alternating current.

19.4     INDUCTOR

An inductor, also known as a coil, choke, or reactor, is a passive electrical component that stores energy in a magnetic field when current flows through it, opposing sudden changes in current.

INDUCTANCE: Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor.

The unit of Inductance is Henry (H).

ENERGY STORED IN AN INDUCTOR: The energy stored in an inductor is given by the formula:

W = (1/2)LI²

Where       W is the energy stored in joules,

L is the inductance in henries, and

I is the current flowing through the inductor in amperes.

 APPLICATIONS/USES OF INDUCTORS – Used in filters, transformers, and energy storage devices.

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          19.5     EDDY CURRENT

Eddy currents are loops of electric current that are induced within conductors by a changing magnetic field. When a conductor (like a metal plate) is exposed to a varying magnetic field, the changing magnetic flux induces currents in the conductor.

These currents flow in closed loops, or “eddies,” which is where the name comes from.

REDUCTION OF EDDY CURRENT -Use laminated cores to reduce eddy currents in transformers.

APPLICATIONS OF EDDY CURRENT – Used in induction heating, braking systems, and metal detectors.