TOPIC 1 - Work-Energy-Heat

Fundamental Physics for Radiographers

• Presenter: Izza Nadia binti Mohd Maulana

• Course Code: RXD12402

• Overview of the course content aimed at supporting radiographers' understanding of fundamental physics concepts.

Subtopics Covered

1. Introduction to Physics

2. Work, Energy, and Power

3. Properties of Electrical Charges

4. Law of Conservation of Energy

5. Heat and Temperature

6. Heat Transfer

7. Heat Energy in X-ray Tube

Learning Outcomes

• At the end of the topics, students should:

  • Describe work, energy (potential and kinetic energy), and power.

  • Understand the law of conservation of energy.

  • Explain electrical charges and Coulomb’s Law.

  • Describe heat and temperature.

  • Explain the processes of heat transfer: conduction, convection, and radiation.

Introduction to Physics

• Definition: Physics involves the study of interactions between energy, matter, space, and time.

• Goal: To provide explanations for various phenomena, from subatomic particles to large-scale movements (e.g., cars, rockets).

Applications of Physics

• Structural stability

• Lighting

• Acoustics

• Electricity

• Heating

• Cooling

• Radioactive dating of rocks

• Earthquake analysis

• Air quality assessment

Physical Quantities & Units

• Defined through measurement methods or calculations.

• Example: Distance and time are measured; speed is derived from these measurements.

• Importance of Standardized Units: Essential for meaningful comparisons of measurements.

Base and Derived Quantities

• Base Quantity: Not derived from other quantities (e.g., mass, length, time).

• Derived Quantity: Resulting from combinations of base quantities (e.g., speed).

Metric Prefixes

• Metric systems simplify unit conversion using powers of 10.

• Convert between units easily using metric prefixes (e.g., kilo, mega, nano).

Displacement vs. Distance

• Displacement: Change in position has both direction and magnitude.

• Distance: The total length of the path traveled, a scalar quantity.

• Example calculations provided for better understanding.

Work, Energy, and Power

• Work (W): Product of force and distance in the direction of the force; expressed as:

  • ( W = F imes d imes \cos(θ) )

• Energy Types:

  • Potential Energy (PE): Energy stored due to position, calculated as ( PE = mgh ).

  • Kinetic Energy (KE): Energy of motion, calculated as ( KE = \frac{1}{2} mv^2 ).

• Explanation of conservation of energy through examples and equations.

Conservation of Energy

• The total energy in a closed system remains constant.

• Example: Kinetic energy + Potential energy at various positions.

• Work-Energy Theorem connection to non-conservative forces.

Power

• Definition: Rate at which work is done or energy is transferred.

• Calculated as:

  • ( Power = \frac{Work}{Time} )

• Unit of Power: Watt (1 W = 1 J/s).

Electrical Charges

• Fundamental property of subatomic particles, associated with forces in electric and magnetic fields.

• Types: Positive (e.g., protons) and negative (e.g., electrons).

• Unit: Coulomb (C).

Properties of Electrical Charges

• Additivity: Charges combine to form net charge.

• Conservation: Total charge is conserved in isolated systems.

• Quantization: Electric charge exists in discrete units, defined as the elementary charge.

Coulomb’s Law

• Explains the electrostatic force between charges.

• Formula:

  • ( F = k \frac{q_1 \cdot q_2}{r^2} )

• Describes relationship among charge magnitudes and distance.

Heat and Temperature

• Heat: Form of energy flowing from hotter to cooler areas, measured in Joules.

• Temperature: Degree of hotness/coldness, measured in Kelvin (K) or Celsius (°C).

• Differences in the definitions and properties of heat and temperature explained.

Specific Heat Capacity

• Defined as the heat required to raise 1 kg of a substance by 1 °C.

• Equation: ( Q = mcΔT ) for heat absorbed or lost.

• Specific heat capacities of various substances provided for reference.

Heat Transfer

• Exchange of thermal energy occurs from hot to cold areas.

• Methods of Transfer:

  1. Conduction: Heat transfer through materials (e.g., iron to clothes).

  2. Convection: Movement of fluids to transfer heat (e.g., boiling water).

  3. Radiation: Heat transfer via electromagnetic waves (e.g., heat from the sun).

Heat Energy in X-ray Tube

• X-ray production involves conversion of kinetic energy of electrons into thermal energy.

• Most kinetic energy becomes heat; less than 1% is converted to x-rays.

• Cooling methods utilize radiation, conduction, and convection.

• Heat unit calculation: ( HU = kVp \times mA \times time(s) ).