AP ECET MECHANICAL ENGINEERING Multiple Choice Questions (MCQs)

AP ECET Mechanical Engineering MCQs (Unit V: Thermodynamics and Heat Power Engineering)

61. Which of the following is an assumption made in the thermodynamics of perfect gases?
    A) Gases behave ideally at low temperatures and high pressures
    B) Gases obey the ideal gas law at all temperatures and pressures
    C) The specific heat capacity of gases is constant
    D) Gases are incompressible
    Answer: C) The specific heat capacity of gases is constant
62. The efficiency of a Carnot engine depends on:
    A) The temperature difference between the hot and cold reservoirs
    B) The pressure difference between the working fluid and surroundings
    C) The specific heat of the working fluid
    D) The type of fuel used in the engine
    Answer: A) The temperature difference between the hot and cold reservoirs
63. In an ideal gas, the internal energy is dependent on:
    A) Temperature only
    B) Pressure only
    C) Volume only
    D) Temperature and volume
    Answer: A) Temperature only
64. Which of the following is the air-standard cycle used in I.C. engines?
    A) Stirling cycle
    B) Rankine cycle
    C) Brayton cycle
    D) Otto cycle
    Answer: D) Otto cycle
65. The compression ratio of an engine is defined as:
    A) The ratio of the maximum volume to minimum volume in the cylinder
    B) The ratio of the minimum volume to the maximum volume in the cylinder
    C) The ratio of the swept volume to the clearance volume
    D) The ratio of the displacement volume to the total volume
    Answer: A) The ratio of the maximum volume to minimum volume in the cylinder
66. The power produced by the engine is the:
    A) Brake power
    B) Indicated power
    C) Friction power
    D) Mechanical power
    Answer: A) Brake power
67. The thermal efficiency of a petrol engine is typically lower than a diesel engine because:
    A) Petrol has a higher energy content
    B) Petrol engines operate at lower compression ratios
    C) Diesel engines operate at lower temperatures
    D) Diesel engines have better lubrication
    Answer: B) Petrol engines operate at lower compression ratios
68. Which of the following is a characteristic of a two-stroke engine?
    A) It requires four piston strokes for a complete cycle
    B) It has an exhaust valve and intake valve
    C) It completes the power cycle in two strokes of the piston
    D) It has a higher efficiency than four-stroke engines
    Answer: C) It completes the power cycle in two strokes of the piston
69. In a diesel engine, the ignition is initiated by:
    A) A spark plug
    B) Compression of the air-fuel mixture
    C) A glow plug
    D) A pilot flame
    Answer: B) Compression of the air-fuel mixture
70. The primary function of an air compressor is to:
    A) Increase the temperature of the air
    B) Reduce the pressure of the air
    C) Increase the pressure of the air
    D) Increase the volume of the air
    Answer: C) Increase the pressure of the air
71. The Brake Thermal Efficiency (BTE) of an engine is the ratio of:
    A) Brake power to the input power
    B) Indicated power to the input power
    C) Brake power to the fuel energy supplied
    D) Indicated power to the fuel energy supplied
    Answer: C) Brake power to the fuel energy supplied
72. A four-stroke engine completes the power cycle in:
    A) Two piston strokes
    B) Four piston strokes
    C) Three piston strokes
    D) Six piston strokes
    Answer: B) Four piston strokes
73. A gas turbine engine works on the principle of:
    A) Otto cycle
    B) Rankine cycle
    C) Brayton cycle
    D) Stirling cycle
    Answer: C) Brayton cycle
74. Jet propulsion is based on the principle of:
    A) Newton's third law of motion
    B) Conservation of energy
    C) Conservation of momentum
    D) Bernoulli's theorem
    Answer: A) Newton's third law of motion
75. The main difference between a petrol and a diesel engine is:
    A) Petrol engines have a higher compression ratio
    B) Diesel engines have a spark plug
    C) Diesel engines are spark-ignited
    D) Petrol engines are compression-ignited
    Answer: A) Petrol engines have a higher compression ratio

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