B-2 Physics Topic 2.3 Thermodynamics

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Questions and Answers

What is the boiling point of water in Kelvin?

273 K

0 K

373 K (correct)

100 K

What does zero on the Kelvin scale represent?

Freezing point of water

Boiling point of water

Absolute zero (correct)

Melting point of ice

Which temperature scale has 180 increments between the freezing and boiling points of water?

Newton

Fahrenheit (correct)

Kelvin

Celsius

What is the formula to convert Celsius to Fahrenheit?

°F = 9/5 °C + 32 Signup and view all the answers

At what temperature does ice begin to melt?

0°C Signup and view all the answers

What is the amount of heat required to melt ice called?

Latent heat of fusion Signup and view all the answers

What happens to the temperature of ice as it melts?

It remains constant Signup and view all the answers

What must happen after ice has melted and heat is added?

Temperature begins to rise Signup and view all the answers

What happens to the temperature of a gas when it is released from a higher pressure to a lower pressure?

The temperature drops considerably. Signup and view all the answers

Which of the following accurately describes the first law of thermodynamics?

Energy can only be converted from one form to another. Signup and view all the answers

What is one application of the second law of thermodynamics?

Using a car radiator to dissipate heat. Signup and view all the answers

What is thermal energy related to?

The application and conversion of heat. Signup and view all the answers

What occurs when fuel undergoes combustion?

Heat is produced, which can be useful or unwanted. Signup and view all the answers

According to the general gas law, what happens when a cylinder is filled too quickly?

The cylinder pressure increases. Signup and view all the answers

What is the primary cause of heat in a substance as described in the kinetic theory of matter?

The kinetic energy of random motion Signup and view all the answers

What is a key characteristic of thermal energy?

It can be created from various other energy forms. Signup and view all the answers

In the case of volumetric expansion, what happens to a solid when it is heated?

It expands in length, breadth, and thickness Signup and view all the answers

Which formula is used to calculate expansion in solids due to temperature changes?

E = kL(T2 – T1) Signup and view all the answers

Which statement about heat flow is true according to thermodynamics?

Heat flows from hotter to colder bodies. Signup and view all the answers

What effect does heating a bi-metallic strip have on its structure?

It bends due to different expansion rates Signup and view all the answers

What role does a bi-metallic strip play in thermostats?

It balances the clock wheel Signup and view all the answers

What is typically not true regarding the expansion of solids?

All solids expand uniformly regardless of substance Signup and view all the answers

Which statement correctly describes molecular movement as temperature increases?

Molecules move further apart with more energy Signup and view all the answers

What happens to the structure of a bi-metallic strip when temperature changes?

It bends due to different expansion rates of metals Signup and view all the answers

What occurs to water when it reaches its boiling point and heat is continually added?

The water evaporates into steam Signup and view all the answers

What is the role of latent heat during a change of state?

It breaks down intermolecular bonds Signup and view all the answers

How much latent heat is required to convert one gram of water at 100°C to steam at 100°C?

540 calories Signup and view all the answers

What is sensible heat defined as?

Heat that can be felt and causes a temperature change Signup and view all the answers

In the refrigeration cycle, what happens to the refrigerant gas when it is compressed?

It heats up due to increased pressure Signup and view all the answers

What happens to one gram of steam at 100°C when it loses 540 calories of heat?

It condenses into water at 100°C Signup and view all the answers

What describes the difference between latent heat and sensible heat?

Latent heat involves breaking bonds, while sensible heat increases kinetic energy Signup and view all the answers

How much sensible heat is needed to raise the temperature of one gram of water from 0°C to 100°C?

100 calories Signup and view all the answers

What is the formula used to calculate work done by an expanding gas?

W = Fs Signup and view all the answers

Which of the following factors affects the power generated by an object?

Time taken to perform work Signup and view all the answers

In an engine cycle, what occurs immediately after the compression of air?

Ignition of fuel Signup and view all the answers

What factor contributes to the increase in temperature of air during compression in an engine?

Increased kinetic activity of molecules Signup and view all the answers

In a piston engine, what is the role of the spark during the power stroke?

To ignite the air-fuel mixture Signup and view all the answers

During which phase of the piston engine cycle is the air and fuel mixture drawn into the cylinder?

Intake Stroke Signup and view all the answers

What happens to the exhaust gases in a piston engine after the power stroke?

They are ejected from the exhaust valve Signup and view all the answers

What is the typical compression ratio of the air and fuel mixture in a piston engine?

15:1 Signup and view all the answers

What characterizes the combustion process in a gas turbine engine operating under the Brayton cycle?

Combustion occurs at constant pressure Signup and view all the answers

Which engine type uses extra turbines to transfer power to a propeller?

Turboprop Signup and view all the answers

In a turbofan engine, what accelerates the air mass?

A multi-bladed fan Signup and view all the answers

What is a primary application of the power delivered by a turboshaft engine?

Electrical generators Signup and view all the answers

According to Newton's second law, how is thrust (F) related to the mass of air and acceleration?

F = m (V - U) Signup and view all the answers

Which statement best describes the mass flow rate of air used in propulsion?

A prop gives a large mass of air with small acceleration. Signup and view all the answers

What is the relationship between air mass flow rate and thrust in gas turbine engines?

Thrust is dependent on both mass flow rate and velocity changes. Signup and view all the answers

What is the primary advantage of the turbofan engine design?

It enhances fuel efficiency with large air mass flow. Signup and view all the answers

Study Notes

Module: B-2 Physics, Topic 2.3 Thermodynamics

Introduction: Students should be able to describe temperature and thermometer operation, define different temperature scales (Celsius, Fahrenheit, Kelvin), and define heat.
Specific Heat and Heat Capacity: Students should be able to define specific heat, describe heat capacity, and understand methods of heat transfer (convection, conduction, radiation).
Thermodynamic Laws: Students should be able to describe volumetric expansion, state the first and second laws of thermodynamics, and describe ideal gases, specific heat at constant volume and pressure, and work done by an expanding gas.
Thermodynamic Processes: Students need to describe isothermal and adiabatic expansion and compression, engine cycles, constant volume and pressure, refrigerators and heat pumps, latent heats of fusion and evaporation, thermal energy, and heat of combustion.
Heat: The smallest particles (atoms, molecules) of substances are constantly moving randomly. Heat is the kinetic energy associated with this motion. More heat energy means faster molecules move. Heat is a form of energy used to do work.
Thermal Energy: Thermal energy refers to energy related to heat transfer (applying, losing, or moving heat). It cannot be created nor destroyed, only converted. Thermal energy can be converted to other forms, including mechanical or kinetic energy and can add energy to chemical reactions.
Laws of Thermodynamics: The first law of thermodynamics is similar to the law of conservation of energy. Heat energy cannot be destroyed, only changed in form. The second law of thermodynamics dictates that heat flows from warmer to cooler bodies.
Heat of Combustion: Heat is produced in combustion (burning of fuel). Combustion types range from a match's flame to a power station furnace. Heat from combustion can be useful or unwanted. This heat can drive a process or cause harm if not properly managed.
Work Done by Expanding Gases: Sometimes heat produced by combustion is used to do work, like forcing a bullet through a barrel. Expanding gases in a turbine or engine create thrust and power. The amount of work is calculated by force times distance.
Engine Cycles: Both piston and gas turbine engines require initial air compression to ignite fuel. Compression increases the air's temperature. The collisions from the molecules and the container's walls increase the kinetic activity, which causes a temperature rise in the compressed gas. The movement and actions of gases in engines are similar to mechanical processes.
Specific Heat: Specific heat of a substance denotes the heat needed to increase the temperature by a degree Celsius for one unit of mass. Specific heat for gases is defined at either constant pressure or constant volume.
Heat Capacity: Heat capacity is the amount of heat needed to raise the temperature of a whole object by one degree Celsius. It can be calculated with mass and specific heat values.
Temperature: Temperature represents the degree of heat possessed by one mass compared to another. Heat flows from hotter to cooler. Example: A cup of coffee at 90°C has less heat than a swimming pool at 20°C.
Temperature Scales: The Celsius scale is divided by 100 increments (freezing point to boiling point). The Kelvin scale measures temperature at which molecular activity stops (absolute zero). The Fahrenheit scale has 180 divisions between the water freezing and boiling points, with the freezing point at 32°F and the boiling point at 212°F.
Thermometers: Bulb thermometers measure temperature based on a liquid's change in volume as it heats or cools, usually mercury.
Latent Heat: Latent heat causes a substance to change state without changing temperature — think ice melting or water boiling.
Latent Heat of Fusion: The amount of heat required to change a substance from a solid to a liquid, without changing the temperature.
Latent Heat of Vaporization: The amount of heat necessary to vaporize a liquid, keeping the temperature constant until complete evaporation.
Constant Volume Engine: The combustion action occurs at approximately constant volume in piston engines.
Constant Pressure Engine: Combustion happens at approximately constant pressure in gas turbine engines.
Types of Engine Cycles: Students should consider turboprops, turbofans, and turboshfts along with Otto Cycle as engine examples. Different methods of deriving thrust are examined.

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Description

This quiz covers the fundamentals of thermodynamics, including temperature measurement and heat concepts. Students will explore specific heat, heat capacity, and the laws of thermodynamics. Additionally, it examines thermodynamic processes and heat transfer methods, providing a comprehensive understanding of the subject.