Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Thermal physics ↓


heat and temperature


In the world around us, you often hear the terms "heat" and "temperature" used interchangeably. However, in the field of physics, these terms have very different meanings. In this explanation, we'll delve deeper into the concepts of heat and temperature, exploring how they are measured, their differences, and their roles in thermal physics. Let's start with a simple definition of each term.

Withstanding temperature

Temperature is a measure of the average kinetic energy of the particles in a substance. Kinetic energy refers to the energy an object has because of its motion. The greater the speed of the particles, the higher the temperature. So, when you measure the temperature of an object, you are essentially measuring how quickly the particles (such as atoms and molecules) are moving.

Temperature measurement

Temperature can be measured using a variety of scales. The most common scales are Celsius, Fahrenheit, and Kelvin.

  • Celsius (°C): On this scale, water freezes at 0°C and boils at 100°C under standard atmospheric conditions.
  • Fahrenheit (°F): On this scale, water freezes at 32°F and boils at 212°F.
  • Kelvin (K): This is the scientific scale used primarily in physics. Zero Kelvin (0 K) is known as absolute zero, the point at which particles theoretically stop moving. Water freezes at 273.15 K and boils at 373.15 K.
warmHotCold0 °C100 degrees Celsius

The above image shows different objects with different lengths. Each length represents a different temperature scale on a thermometer indicating hot, warm, and cold objects.

Examples of temperature

Consider a hot coffee mug and a glass of cold water. When you touch the mug of coffee, it feels hot because the particles in the coffee are moving very fast, indicating a higher temperature. In contrast, when you touch the glass of cold water, it feels cold because the particles are moving slower, indicating a lower temperature.

Understanding the heat

Heat, on the other hand, is energy that is transferred from one object to another due to a difference in temperature. It is the process by which energy moves due to a temperature difference. Heat always flows from a region of higher temperature to a region of lower temperature until thermal equilibrium is reached.

Measurement of heat

In the International System of Units (SI), heat is measured in joules (J). However, in everyday life, you may be familiar with calories, which is another unit used to measure heat.

  • Joule (J): The standard measure of energy. 1 joule is the energy transferred when 1 watt of power is applied for 1 second.
  • Calorie (cal): Often used in reference to food, 1 calorie is the energy needed to raise the temperature of 1 gram of water by 1°C.

Examples of heat transfer

Consider the following scenario:

  • Conduction: When you hold a metal spoon in a hot pot of water, the heat of the water is transferred to the spoon, eventually heating the part you're holding.
  • Convection: When water is heated in a vessel, the bottom layer heats up first. The hot water rises and cooler water moves down to take its place, creating a circulating motion.
  • Radiation: The warmth you feel from the Sun, even though it is millions of kilometres away, is due to heat transferred through radiation.
SunRadiator

The figure shows different sources of heat (sun and radiator) transferring energy. The arrows indicate the direction of heat transfer.

Difference between heat and temperature

It is important to distinguish between heat and temperature because they are not the same thing. Below are some key differences:

  • Nature: Temperature measures the average kinetic energy of particles, while heat refers to the energy transferred due to temperature differences.
  • Measurement units: Temperature is measured in Celsius, Fahrenheit, or Kelvin, while heat is measured in joules or calories.
  • Conceptual understanding: Temperature is a scalar quantity that indicates the degree of hotness or coldness of an object. Heat is an energy form that can be transferred and is considered a transient form - meaning it is not stored in an object.

Mathematical relationships

The heat transferred to or from an object can be calculated using the following equation:

Q = mcΔT

Where:

  • Q = heat energy absorbed or released (joules)
  • m = mass of the object (in kilograms)
  • c = specific heat capacity (joules per kilogram per degree Celsius)
  • ΔT = Change in temperature (°C)

Example problem

Let us consider a practical example to solidify our understanding:

How much heat is required to raise the temperature of 2 kg of water from 20°C to 100°C, given that the specific heat capacity of water is 4.18 J/g°C?

Solve using the formula:

Q = mcΔT

Convert the specific heat capacity to J/kg°C by multiplying it by 1000:

  • Specific heat capacity (c): 4.18 J/g°C x 1000 = 4180 J/kg°C

Substitute into the formula:

Q = (2 kg) x (4180 J/kg°C) x (100°C - 20°C)
Q = 2 x 4180 x 80
Q = 668800 joules

Thus, 668,800 joules of heat are required to raise the temperature of the water.

Conclusion

Understanding the difference between heat and temperature is important in the study of thermal physics. Temperature gives us information about the kinetic energy level of particles within an object, while heat represents the transfer of energy from one entity to another. By understanding these concepts, we improve our understanding of how energy moves and how it is used in various fields, from the boiling of water to the functioning of engines and beyond.


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