Power can be transmitted in many ways, such as belts, ropes, chains and couplings, but gears are a very important part of power transmission. With the help of gears, a defined speed ratio is obtained and they have found applications in many machines such as automobile transmission, machine tools, rolling mills and clocks. A gear is a circular toothed part that meshes with another toothed part to provide a specific output. The output can be in the form of speed or torque. The purpose of the protrusions or teeth is to reduce slippage. Two or more gears working together are called a gear train. Meshed gears always rotate in opposite directions.Fig.4.1 Meshing of two gearsGears of different sizes can be combined to design different mechanisms according to particular needs. Gears are generally designed to avoid failure due to static and dynamic loads. Gears can be made of cast iron, steel, bronze, phenolic resin, nylon and Teflon, etc. The main advantages of gear drives include transmission of exact gear ratio, high efficiency and compact layout.4.2 HISTORY OF GEARSGears are as old as any other machine. , humanity uses. The early Greeks and Romans made extensive use of gears. The Antikythera Mechanism is an example of an ancient gear-driven device designed to calculate astronomical positions (built between 150 and 100 BC). The first known gear mill was built around 27 BC. In the fourth century BC, Aristotle wrote about wheels using friction between smooth surfaces to transmit motion. Early humans used wooden gears to grind wheat and hammer metals. During the early Christian era, gears were used in many machines such as clocks, waterwheels, and windmills. Philo of Byzantium, A...... middle of paper ......the cudgel shape used in gears today is as followsa) Involute profileb) Base circlec) Convolute profile) None of the above -above3. Gear teeth formed on a flat surface are called thisa) Pinionb) Straight) Rackd) Teeth4. These gears transmit power between shafts whose axes intersect at any angle:a) Worm gearsb) Spur gearsc) Bevel gearsd) Rack and pinion5. What gears are used when large reductions in speed and increases in power are required?a) Spurb) Wormc) Beveld) rackShort answer questions1. Explain the procedure adopted to calculate the speed ratio of the epicylic gear train.2. What do you mean by i) addendum ii) module iii) Pitch circle3. Write a short note on the law of gearing.4. Classify different types of gears and their applications.5. What are the advantages of gear drives over other power transmission methods??