Republic of the Philippines Doc. Ref. No.
:
Effectivity
ABRA STATE INSTITUTE OF SCIENCES AND TECHNOLOGY 0
Date:
Main Campus, Lagangilang, Abra Revision No.: 0
College of Agriculture Forestry and Cooperatives Page No.:
Name: ___________________ Score: _____________
Course & Year: ____________ Date: ______________
MIDTERM EXAM
Agri Tech 114 (Agricultural Mechanics)
I. Direction: multiple choice (35 pts.) read and analyze the questions briefly. Encircle the letter that
you may fix the questions. Answers with erasures and overwriting will be considered wrong.
1. Hydropower generates electricity by harnessing the energy of:
A) Ocean waves B) Tides
C) Rivers or waterfalls D) Geothermal reservoirs
2. Which renewable energy source is considered intermittent and variable in its generation?
A) Geothermal energy B) Biomass energy
C) Solar power D) Hydropower
3. What is a key advantage of using renewable energy sources in farming and agriculture?
A) Increased dependence on fossil fuels B) High energy costs
C) Improved energy security D) Limited technological advancements
4. What is a key advantage of using renewable energy sources in farming and agriculture?
A) Increased dependence on fossil fuels B) High energy costs
C) Improved energy security D) Limited technological advancements
5. How many thermal efficiency of diesel engine
A) 32- 28% B) 22 – 38%
C) 32 – 38% D) 32 – 25%
6. Which engine component is responsible for converting reciprocating motion into rotary
motion?
A) Carburetor B) Camshaft
C) Crankshaft D) Piston
7. What is the purpose of the fuel injection system in modern engines?
A) To ignite the fuel-air mixture B) To compress the fuel-air mixture
C) To deliver precise amounts of fuel D) To control exhaust emissions
8. What role does the radiator play in an engine cooling system?
A) To regulate fuel temperature B) To filter impurities from oil
C) To dissipate heat from coolant D) To lubricate moving parts
9. Which type of lubricating system uses a pump to circulate oil to various engine parts?
A) Splash lubrication B) Dry sump lubrication
C) Wet sump lubrication D) Manual lubrication
10. What is the primary purpose of a fuel injector in a modern fuel system?
A) To filter contaminants from the fuel B) To mix air and fuel
C) To atomize and deliver fuel into the combustion chamber D) To store fuel
11. Biofuels are derived from:
A) Animal waste B) Human waste
C) Plant matter D) All of the above
12. Solar panels convert sunlight directly into:
A) Heat energy B) Mechanical energy
C) Chemical energy D) Solar power
13. What is the primary purpose of an engine combustion chamber?
A) To store fuel B) To compress air
C) To mix air and fuel D) To ignite fuel-air mixture
14. In a four-stroke engine, how many strokes are needed to complete one combustion cycle?
A) 1 B) 2
C) 3 D) 4
15. The exhaust valve opens during which stroke of a four-stroke engine?
A) Intake B) Compression
C) Power D) Exhaust
16. In a 4-stroke engine, which stroke is responsible for the intake of the air-fuel mixture?
A) Compression stroke B) Power stroke
C) Exhaust stroke D) Intake stroke
17. Which engine component is responsible for converting reciprocating motion into rotary
motion?
A) Carburetor B) Camshaft
C) Crankshaft D) Piston
18. What is the purpose of the fuel injection system in modern engines?
A) To ignite the fuel-air mixture B) To compress the fuel-air mixture
C) To deliver precise amounts of fuel D) To control exhaust emissions
19. What role does the radiator play in an engine cooling system?
A) To regulate fuel temperature B) To filter impurities from oil
C) To dissipate heat from coolant D) To lubricate moving parts
20. What is the primary function of the piston in both 2-stroke and 4-stroke engines?
A) To ignite the fuel B) To create a vacuum for air intake
C) To compress the air-fuel mixture and convert pressure into rotational energy
D) To expel exhaust gases
21. The combustion stroke in an engine occurs after which stroke?
A) Intake B) Compression
C) Power D) Exhaust
22. What is the main advantage of a 2-stroke engine compared to a 4-stroke engine?
A) Higher fuel efficiency B) Simplicity and lighter weight
C) Lower emissions D) Longer lifespan
23. What engine component converts the up-and-down motion of the piston into rotational
motion?
A) Carburetor B) Crankshaft
C) Camshaft D) Flywheel
24. What type of engine uses spark plugs to ignite the fuel-air mixture?
A) Diesel engine B) Gasoline engine
C) Rotary engine D) Turbine engine
25. Which of the following is a renewable source of energy derived from the sun's radiation?
A) Natural gas B) Solar
C) Coal D) Petroleum
26. Biomass energy is derived from:
A) Fossil fuels B) Agricultural and forest residues
C) Nuclear reactions D) Geothermal heat
27. Which renewable energy source relies on capturing the natural flow of rivers and oceans to
produce electricity?
A) Solar power B) Tidal power
C) Biomass energy D) Geothermal energy
28. What is a major advantage of using biomass energy in agriculture?
A) High initial installation cost B) Reliable and consistent energy supply
C) Limited availability of feedstock D) Dependence on fossil fuel backup
29. Which renewable energy source can be used to generate electricity without producing
greenhouse gas emissions?
A) Biomass energy B) Hydropower
C) Tidal power D) None of the above
30. The process of converting wind energy into electricity involves which technology?
A) Solar panels B) Wind turbines
C) Geothermal wells D) Biomass gasifiers
31. Which renewable energy source is used in conjunction with traditional agriculture to reduce
waste and generate power?
A) Wind power B) Biomass energy
C) Solar power D) Geothermal energy
32. Which renewable energy source is considered most suitable for off-grid applications in
remote agricultural areas?
A) Wind power B) Solar power
C) Tidal power D) Biomass energy
33. The crankshaft in an engine converts linear motion into:
A) Electrical energy B) Mechanical energy
C) Thermal energy D) Chemical energy
34. What is the purpose of engine lubrication systems?
A) To cool the engine B) To reduce friction between moving parts
C) To control fuel flow D) To filter exhaust gases
35. What is the primary function of a radiator in an engine's cooling system?
A) To increase engine temperature B) To dissipate heat from the coolant
C) To circulate oil D) To filter fuel
36. In which cooling system is a mixture of water and antifreeze commonly used?
A) Air cooling B) Liquid cooling
C) Evaporative cooling D) Thermoelectric cooling
37. How many percent removed by water cooling system
A) 40% B) 30%
C) 20% D) 10%
38. How many best operating Temperature of IC engines
A) 1700ᵒC B) 1600ᵒC
C) 1500ᵒC D) 1400ᵒC
39. Which parts of IC engine requires for lubricants EXCEPT one.
A) Piston pin B) Radiator
C) Cooling fan D) Camshaft bearings
40. Which pats of fuel system in Diesel engine EXCEPT one
A) Fuel filter B) Carburetor
C) Fuel injection pump D) Fuel lift
41. The purpose of lubrication in the IC engine are.. EXCEPT one
A) Cooling effect B) Hot effect
C) Cleaning effect D) Sealing effect
42. Which of the following is a characteristic of a 4-stroke engine?
A) Requires a separate lubrication system B) Produces a power stroke with every revolution of
the crankshaft
C) Typically has a simpler design D) Lower RPM capabilities
43. Which engine component is responsible for ensuring proper sealing between the cylinder
head and the engine block?
A) Piston rings B) Connecting rod
C) Valve spring D) Timing belt
44. Which renewable energy source is most commonly used for heating water and buildings in
rural areas?
A) Solar power B) Wind power
C) Biomass energy D) Geothermal energy
45. How many power strokes occur in one complete cycle of a 2-stroke engine?
A) One B) Two
C) Three D) Four
II. Instruction: Problem computation (15pts.) read carefully and analyze the problem. Show
your computation.
1. A gasoline engine has a thermal efficiency of 30%. The engine generates 120 KW of
useful power output. Calculate the rate at which heat is rejected to the exhaust.
Solution:
Ƞ = 30%
Useful power output Pout = 120 KW
Ƞ = Pout
Qin
Qin = Pout
Ƞ
Qin = 120 kw = 400 kw
0.30
Qout = Qin – Pout
Qout = 400 kw – 120 kw
Qout = 280 kw
2. A steam engine operates with a heat input of 5000 kJ and expels waste heat of 2000 kJ.
Calculate the thermal efficiency of the engine.
Solution:
Heat Input (Qin) = 5000 kJ
Waste Heat (Q out) = 2000 kJ
The useful work output (W) can be calculated as:
W = Q in – Q out = 5000kJ - 2000kJ = 3000kJ
Ƞ = W / Q in = 3000 kJ / 5000 kJ = 0.6
3. An internal combustion engine consumes 8000 kJ of fuel and produces 2800 kJ of useful
work. What is the thermal efficiency of the engine?
Solution:
Heat Input Q in = 8000 kJ
Useful Work Output (W) = 2800 kJ
Ƞ = W/ Q in = 2800 kJ / 8000 kJ = 0.35
4. If a heat engine has an efficiency of 25% and absorbs 1,000 J of heat, how much heat is
rejected?
Solution:
Work output = ƞ x Qin = 0.25 x 1000 J = 250 J
Q out = Q in - W = 1000 J - 250 J = 750 J
5. A 4-stroke cycle engine consumes 2.5 kg of fuel per hour, which has a calorific (high
energy) value of 42,000 kJ/kg. The engine produces 40 kW of useful work output.
Calculate the thermal efficiency of the engine.
Given:
Fuel consumption (m) 2.5 kg/h (unit of fuel consumption is in kg/s)
Calorific value (CV) 42,000 kJ/kg
Power output (Pout) 40 kW
1. Calculate the heat input Qin
Qin = m x CV
First, convert the fuel consumption to seconds (since power is in kW):
Fuel consumption in kg/s = 2.5 kg/h / 3600 s/h = 0.000694kg/s
Now, calculate the heat input:
Qin = 0.000694 kg/s x 42,000 kJ/kg = 29.188 kJ/s = 29.188 kW
2. Calculate thermal efficiency (η)
Ƞ = Pout_
Qin
Substituting the values:
Ƞ = 40 kW x 100%
29.188 kW
Ƞ = 1.37
