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Heat Engine–10th Science Learning Cards


Heat Engine

Learning Card-1

I. Choose the correct answer:

1. This represent the cylinder and piston in a heat engine


2. The part in a steam engine which converts linear motion into rotation

a)Inlet value b) cylinder c) outlet value d)crankshaft

3. First commercial steam engine was designed by

a) James Watt c) Thomas Savery c)Thomas cook d) Newton

4. the improved steam engine with cylinder and values was designed by

5. a) Thomas savery b) Carl diesel c) James Watt d) Thomas Edison

6. Rudolf Diesel and Nicholas otto are credited to designing

a) Steam engine b) External combustion engine

c) Railway steam engine d) internal combustion engine

II. Answer in a Sentence.

1. What is heat engine?

A heat engine is a device which converts heat energy into mechanical energy.

2. Name the two types of heat engine.

a. External combustion engine b. Internal combustion engine.

3. What is the effect of heat?

a. Increase in the temperature of a body. b. Expansion of the body

c. change of state of matter d. chemical change in the body

4. Name the two types of movements of Air flow.

Air flow has two type of movements.

a. random movement of molecules within the system.

b. Enmass laminar flow along the direction of flow.

5. What is balanced force?

If net resultant force is zero then is called as balanced force.

6. Who designed steam engine?

Thomas savery designed commercially useful steam engine.

7. What is eternal combustion engine?

Engine which burns the fuel outside is called eternal combustion engine.

8. Draw a neat label diagram of expansion stroke.


9. Draw a neat diagram of Exhaust stroke.


10. Draw a labelled diagram of petrol engine.


11. Define the function of Crank shaft.

Crank shaft coverts linear movement into circular motion. The wheel of the crank shaft makes half rotation during the expansion stroke.

12. Define the function of Petrol engine.

Spark plug:- The compressed air and petrol mixture is ignited by the sparks produced by the spark plug.

Crank shaft:- crank shaft coverts linear movement into circular motion.

Carburetor:- In the carburetor petrol and air are mixed in proper proportions.

Outlet valve:- makes the spent gases to go out of cylinder.

13. Define the 5 stages of working petrol engine.

a. Intake stroke:- The vapourised mixture of petrol and air is let in through the inlet value. The outlet value remains closed. Piston moves away from the spark plug.

b. Compression stroke:- Both the values are closed and the mixture of air and petrol is compressed by the piston moving towards the spark plug. Though the compression increases the temperature of the mixture it is not sufficient to ignite the petrol.

c. Power stroke:- The ignition stage and the expansion stage are together called power stroke.

d. Exhaust stroke: Here outlet value opens Piston moves back. The products of combustion gases are pushed out of the cylinder through the exhaust value.


Learning Card-2

1. The kick start in petrol engine would produce

(a)High pressure inside the cylinder (b)Low pressure inside the cylinder

(c)Ignites the fuel in intake stroke (c)Sends the waste gases out of cylinder

2. The efficiency of a heat engine is 40%. If you want to get a work of 200KJ, the amount of heat energy to be supplied is

(a)200KJ (b)500KJ (c)2000KJ (d)800KJ

3. The main reason that steam engine cannot be used in small vehicles is

(a)Less efficiency (b)More cost (c)Bulky by structure (d)Chance of bursting

4. The reason, that diesel engine is preferred to petrol engine is

(a)Comparatively petrol does not undergo combustion completely

(b)Cost of petrol is more

(c)Diesel engines cost more

(d)Petrol releases more energy than diesel


Learning Card-3

Choose the correct answer:

1. The heat engine which converts latest heat into mechanical energy is

a) Petrol engines b) Diesel engine c) Steam engine d) All the above

2. The type of heat engine used in a bike would be

a) Steam engine b) petrol engine c) Diesel engine d) Any of the above

3. Petrol and air mixture is compressed in a petrol engine.

a) To get more mechanical energy b) To increase the temperature

c) To mix fuel and air properly d) To ignite the fuel

4. A heat engine is 20% efficient If 200KJ is supplied the height to which it can lift an object of mass 2kg is near the surface of the earth is

a) 1.04 m b) 2.04 m c) 3.04 m d) 4.04 m

5. If a heat engine whose efficiency is 50% is supplied with a heat of 5000KJ the work done is

a) 2500KJ b) 1250KJ c) 10000KJ d) 2000KJ

Answer in a Sentence.

1. A heat engine has a efficiency of 50%. How high it can lift a object of mass 7kgs when it is supplied with a heat energy of 550KJ (g=9.8ms-2)

2. An engine lifts an object of mass 5kg to a height of 100m if its efficiency is 30% calculate the heat energy to be supplied? (g=10ms-1)

3. Why diesel engine is more efficient than petrol engine?

Diesel engine has more compression ratio than petrol engine and also the amount of heat liberated by the combustion of diesel is more hence, diesel energy has more efficiency

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