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The common ostrich is a large, flightless bird that lives in Africa. It is a record breaker in many ways; not only is it the biggest, tallest and heaviest bird, it’s also the fastest bird on land, the fastest two-legged animal, and it lays the largest eggs of any animal. The common ostrich is a […]
Chimpanzees look a little like monkeys, but chimps don’t have tails, whereas monkeys do. In fact, this is the main different between apes and monkeys. Apes are also generally bigger than monkeys. Next time you go to a zoo, remember to check for a tail to know if you’re looking at a monkey or an […]
The cheetah is one of Africa’s most famous animals. Most people in the world are able to identify this elegant, long legged cat with its golden, spotted coat. The cheetah’s Latin name is Acinonyx jubatus. It is one of the larger members of the felidae (cat) family. However, as we’ll see further down the page, […]
The blue whale is a marine mammal. Its scientific name is Balaenoptera Musculus. Like all mammals, blue whales are warm-blooded, breathe air and even have some hair on their bodies! Blue whales are known for their extremely large size – an average male weighs a huge 190,000 kgs (190 tonnes). Despite their huge size, blue […]
Blue morphos are large, brilliant blue butterflies that live in the forests of South and Central America, and also in parts of North America. Due to their striking looks and size, they are one of the best-known butterflies, and a favorite rainforest species. Blue Morphos, like all other butterflies, have three main body parts: the […]
African Elephant African Elephants are the world’s largest land animal. These gentle giants can be distinguished from their Indian counterparts by their huge ears. African elephants can reach heights of 13 feet (4 meters) at the shoulder. They can weigh as much as 14,000 pounds (6,350 kilograms). There are two species of African elephant: the […]
Compact Fluorescent Lamp (CFL) The compact fluorescent lamps are becoming very useful nowadays, because of consumption of power, cost, longer life, attractive look, smooth light and low maintenance. These lamps are available in different sizes and designs. They have single rod, double rod, triple rod or spiral rod. These lamps are available in different power […]
Fluorescent lamp It is a low pressure mercury vapour lamp. It consists of a glass tube 25 mm in diameter and 0.6 m, 1.2 m and 1.5 m in length. The inner portion of the tube is coated with phosphorous. The tube contains argon gas at low pressure and a drop of mercury is added. […]
Mercury vapour lamp On the basis of pressure inside the discharge tube, the mercury vapour lamps are classified as High pressure mercury vapour lamp and Low pressure mercury vapour lamp. High pressure mercury vapour lamps are classified as: 1. MA type (Mercury vapour lamp with auxiliary electrode) These are operated at 220 ‐ 250 volt, […]
Sodium vapour lamp Sodium vapour lamps are some of the most efficient lamps in the world. They have an efficiency of up to 190 lumens per watt compared to an incandescent street lamp which has between 15 and 19 lumens per watt. This sodium vapour lamps comes in two major groups: 1. High pressure sodium […]
Incandescent lamp The filament of this lamp is heated up to the incandescent stage of heat. So these types of lamps are called as incandescent lamps. There are two types. 1. Vacuum type lamp and 2. Gas filled type lamp In this type of lamp, the sphere shaped glass cover is used. The glass stem […]
Arc lamp The principle of an arc lamp is that when two electrodes carrying current are separated through a small distance, an arc is struck between them. The arc lamps were used in the past for street lighting purposes but nowadays these are used when extreme brightness is required. Carbon arc lamp is most commonly […]
Laws of illumination The illumination on a surface depends upon the luminous intensity, distance between the source and surface and the direction of rays of light. It is governed by following laws. 1. Inverse square law 2. Lambert’s cosine law Inverse square law It states that the illumination of a surface is inversely proportional to […]
Introduction Almost all human activities are based on light. Natural light is obtained from the sun. Artificial light plays an important role in our everyday life. In places where natural light is not available, artificial light is obtained by electric lamps. Lighting plays an important role because of its belief, consistency, simple control and low […]
Difference between Overhead line and Underground cables
Three phase cable Commonly, underground cables are used to transmit three phase power supply. For three phase service, the following cables are used. a. Belted cable up to 11 KV b. Screened cable 22KV to 66 KV c. Pressure cable above 66 KV a. Belted cable up to 11 KV The crosssection view of the […]
Classification of cables a. According to the rating of voltage the cables are classified into i. Low tension cables up to 1 KV ii. High tension cable up to 11KV iii. Super tension cables 22 KV to 33KV iv. Extra high-tension cables 33KV to 66 KV v. Oil filled cables 66KV to 132 KV vi. […]
Underground cables By using underground cable, the power is transmitted from the generating station to the consumers. When electrical power is unable to transmit by overhead lines or in a thickly populated area, underground cables are used. An underground cable consists of one or more conductor covered with suitable insulation and surrounded by a protecting […]
Power distribution system The medium voltage transformer using transmission lines are reduced by step down transformer (415V, or 240V) are used to the consumer. This system includes the feeder lines, distributors and service mains. Feeder line The feeder line is nothing but similar as power transmission conductors. It connects the power from sub-station and power […]
Types of insulators i. Pin type insulator ii. Suspension insulators a. Hewlett suspension type b. Cemented cap type c. Core and link type iii. Strain insulator iv. Shackle insulator v. Stay type insulator i. Pin type insulator This type of insulator is fixed in the crossing arm of the pole. The conductor is placed in […]