Home » Paragraph Writing » Paragraph on “How does a Car Engine work?” complete paragraph for Class 9, Class 10, Class 11 and Class 12

Paragraph on “How does a Car Engine work?” complete paragraph for Class 9, Class 10, Class 11 and Class 12

How does a Car Engine work?


The four pictures on the right show you what happens in a car engine. In the first diagram the piston moves down and sucks fuel in through the inlet valve. Next the piston moves up, squeezing the petrol and air mixture into the top of the cylinder. Then a spark from the sparking plug makes the fuel explode. It forces the piston down, driving round the ‘crankshaft’ it is connected to. Finally the piston rises again, pushing the hot, burnt gases out of the exhaust valve. The valves and the sparking plug are linked to the crankshaft so that they work at the right time. This engine is called ‘four-stroke’ because of the four different stages — inlet, compression, explosion and exhaust. A car engine has several cylinders and all the pistons are connected to the same crankshaft. This is connected to the wheels through the clutch and gearbox.

Most motor-cycles use a simpler ‘two-stroke’ engine. Trucks often use diesel engines which are more powerful and use cheaper fuel. A diesel engine has no sparking plug. Instead the piston compresses the fuel so hard that it explodes on its own. Both petrol and diesel engines are called `internal combustion’ engines because they burn their fuel inside the cylinders to give power. ‘External combustion’ engines like steam engines burn their fuel outside, boiling water into steam to drive the pistons. Internal combustion engines are more convenient but their disadvantage is that the exhaust gases are poisonous.


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