Dynamo is the name given to D.C generators. In the past, alternating current generators are not common. Voltages are generated using dynamo where the voltage generated are later converts to A.C. The dynamo I constructed had a permanent magnet. This magnet in the form of circular disc which revolves around turns of coil that is wound on a u-shaped former. When the disc is rotated the magnetic field North / South pole cuts lines of force and e.m.f is generated.

INTRODUCTION

1.0 BACKGROUND OF THE STUDY

The word Dynamo from “(from the Greek word dynamics: meaning power) was originally another name for an electrical generator and still has some regional usage as a replacement for the word generator. After the discovery of the AC generator and that alternating current can be used as a power supply. The word dynamo became associated exclusively with the communicated direct current electric generator while on AC electrical generator using either ship rings or rotor magnet would become known as an alternator.

A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry and the foundation upon which many other later electric power conversion devices were based including the electric motor, the alternating current alternator and the rotary converter. Today the simple alternator dominates large scale power generation for efficiency, reliability and cost reasons.

A dynamo has the disadvantages of a mechanical commutator besides; converting alternating current to direct current using power rectification devices (vacuum tube or more recently solid state.) is effective and usually economical.

The faraday disk was the first electric generator. the horseshoe shape magnet (A) created a magnetic field through the disk (D) when the disk centers toward the rim. The current flowed out through the sliding spring contact m, through the external circuit and back into the centre of the disk through the axle. The operating principle of electromagnetic generators was later called Faraday’s law, is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux. He also built the first electromagnetic generator, called the Faraday- disk, a type of homopolar generator, using a copper disk rotating between the poles of a horseshoe magnetic. It produced a small DV voltage. This was not a dynamo in the current sense, because it did not use a commutator. This design was inefficient, due to self counseling counter flows of current in regions that were not under the influence of the magnetic field. While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field. This counter flow limited the power output to the pickup wires and induced waste heating the copper disk later, homopolar generators would solve the problem by using an array of magnets arranged around the disk perimeter to maintain a steady field effect in one current flow direction.

Another disadvantage was the output voltage was very low, due to the single current path through the magnetic flux. Faraday and others found that higher, more useful voltages could be produced by winding multiple turns of wire into coil. Wire windings can conveniently produce any voltage desired by changing the number of turns? So they have commutator to produce direct current. Independently of Faraday, (The Hungarian) Anyas Jedlik started experimenting in (1827) with the electromagnetic rotating devices which he called electromagnetic self-rotors. In the prototype of the single pole electric starter, both the stationary and the revolving parts were electromagnetic.

About 1856 he formulated the concept of the dynamo about six years before Siemens and Wheatstone but did not patent it as he thought he was not the first to realize this. His dynamo used, instead of permanent magnets, two electromagnets placed opposite to each other to induce the magnetic field around the rotor, it was also the discovery of the principle of dynamo self excitation.