The Theory of operation of Transformer

Written by Bobby Sunday, 05 July 2009 10:05

A big advantage of A.C. transmission is the ability to easily change voltage by means of a transformer. As there are no moving parts maintenance is very low and efficiency very high ( typically 98%).

Relays and Solenoids

Written by Bobby Sunday, 05 July 2009 09:49

The wire coil of the electromagnet, without its core of magnetic material is called the solenoid. If this solenoid is provided with a movable soft iron core and current flows through the turns of the coil , the magnetic field tends to pull the plunger in to the centre of the coil. Accordingly the coil with its moving centre is called the solenoid.

Types of Fluorescent Lights

Written by Bobby Sunday, 05 July 2009 09:41

Discharge lamps
Cold cathode type-only used for decorative lighting
Hot cathode

• a, High pressure fluorescent

(i)Mercury vapour types) Used mainly for street lighting
(ii) Sodium type , ) but sometimes used for deck lighting

• b, Low pressure Hot Cathode Fluorescent type discharge Lamp
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The Operation of Navigation Lighting System

Written by Bobby Sunday, 05 July 2009 09:33

When the double pole switch is closed the navigation light is illuminated. Current in the relay circuit causes the relay coil to energise so contact 'a' ,may be attracted to 'b'.