Physics Chapter on Heat and Waves

Unit 1, Part 1: Energy

• Energy is the ability to do work
• Work happens when motion occurs in the direction of the applied force
• Energy is measured in Joules (J)
• Two main types of energy are kinetic and potential

Energy Types

• Chemical
• Electrical
• Electromagnetic
• Mechanical
• Nuclear
• Radiant/Light
• Sound
• Thermal

Kinetic Energy

• Kinetic energy is the energy of motion
• Kinetic energy depends on mass and speed
• The faster an object moves, the more kinetic energy it has
• The more massive an object is, the more kinetic energy it has
• Forms of kinetic energy: mechanical, electromagnetic, sound, thermal, light/radiant

Potential Energy

• Potential energy is stored energy due to position
• Example: a boulder on a cliff has gravitational potential energy due to its height
• Forms of potential energy: nuclear, chemical, gravitational, elastic

Energy Relationships

• Energy is never created or destroyed, only transferred
• When a boulder falls off a cliff, its gravitational potential energy converts to kinetic energy
• When a ball is thrown upwards, kinetic energy converts to gravitational potential energy at its highest point
• As the ball falls, potential energy converts back into kinetic energy

Energy Transformation

• The law of conservation of energy states that energy cannot be created or destroyed, only changed from one form to another
• Energy takes many forms
• PE = KE (within a system)
• Mgh = 1/2mv² (within a system)

Unit 1, Part 2: Thermal Energy

• All matter is made of atoms and molecules that are always in motion
• Temperature is the average kinetic energy of a substance
• The faster the particle motion, the higher the temperature
• The slower the particle motion, the lower the temperature
• Different states of matter and particle motion include: solid, liquid, gas

Heat Transfer

• Heat transfer is the movement of thermal energy from hot to cold materials
• Heat always moves from hotter to cooler materials
• There are three types of heat transfer: conduction, convection, radiation

Conduction

• Conduction is heat transfer when objects are in direct contact

Convection

• Convection is heat transfer in fluids by circulation—hot fluids rise, and cold fluids sink in a cycle

Radiation

• Radiation is heat transfer through electromagnetic waves

Conductors & Insulators

• Conductors conduct thermal energy well (e.g. silver, aluminum foil, gold, copper)
• Insulators do not conduct thermal energy well (e.g. air, glass, plastic, rubber)

Specific Heat

• Specific heat is the amount of energy needed to change the temperature of 1 kg of a substance by 1°C
• The lower the specific heat value for a substance, the faster it heats up or cools down
• The higher the specific heat value for a substance, the slower it heats up or cools down

Unit 2 - Waves

• Wave diagrams include crest, trough, wavelength, amplitude, and rest position
• Different wave types have different characteristics (e.g. mechanical waves require a medium to travel, electromagnetic waves do not)
• Mechanical waves include: compression, rarefaction, and transverse

Mechanical & Electromagnetic Waves

• Mechanical waves require a medium to travel. Examples include sound and water waves
• Electromagnetic waves do not require a medium to travel. Examples include light and radio waves

Amplitude & Frequency

• The amplitude of a wave is the distance from the rest position to the crest or trough
• The greater the amplitude, the greater the energy the wave carries
• Frequency is the number of waves that pass a given point per unit of time

Wave Speed Equation

• Wave speed is determined by multiplying frequency and wavelength
• The wave speed equation is: v=f⋅λ where
• v = speed, f = frequency, and λ = wavelength

Reflection & Refraction

• Reflection is the bouncing back of a wave off a surface
• Examples of reflection include echoes from sound waves and colors from light waves
• Refraction is a change in the direction of a wave as it passes from one medium to another
• Examples of refraction include a pencil appearing bent when it's in water and prisms

Diffraction & Interference

• Diffraction is the bending of waves as they pass around a barrier or an opening
• Interference happens when two waves meet while traveling along the same medium
• Constructive interference occurs when waves are displaced in the same direction
• Destructive interference occurs when waves are displaced in opposite directions

Media & Wave Speed

• Medium has the largest effect on wave speed
• Sound waves travel fastest in solids and slowest in gases
• Light waves travel fastest in a vacuum and slowest in solids

Doppler Effect

• The Doppler effect is the apparent change in the frequency of a sound caused by the motion of either the listener or the sound source
• The frequency of a sound increases as the source approaches a stationary observer, and decreases as the source moves away

Unit 3 - Electromagnetism

• Electromagnetism is the interaction between electricity and magnetism
• Magnetic fields are created by electrical currents
• Electrical currents create magnetic fields

Circuits

• An electric circuit is a complete, closed path through which electric charges flow
• All circuits must have three basic parts: an energy source, wires, and a load
• Switches are not necessary but useful components and functional for circuits

Series & Parallel Circuits

• In series circuits components connected in a single loop; all loads share the same current; the addition of another load decreases the overall voltage.
• In parallel circuits components are connected on separate paths or branches; individual loads have the full voltage available; the inclusion of loads does not affect other loads

Schematic Circuit Diagrams

• Schematic circuit diagrams use standardized symbols to represent circuit components

Voltage, Current, & Resistance

• Voltage is the amount of potential energy between two points in a circuit
• Voltage is measure in volts(V)
• Current is the rate that electricity flows, measured in amperes (A)
• Direct Current is in one direction, Alternating Current change direction constantly.
• Resistance is the opposition of flow in a circuit, measured in ohms (Ω)

Ohm's Law Calculations

• Ohm's Law (V = I ⋅ R) relates voltage (V), current (I), and resistance (R) in a circuit

Motors & Generators

• Electric motors convert electrical energy into mechanical energy
• Electric generators convert mechanical energy into electrical energy

Unit 4 – Motion, Force, & Work

Speed & Velocity

• Speed is the distance covered per unit of time, measured in m/s
• Velocity is speed in a specific direction, also measured in m/s

Acceleration

• Acceleration is the rate of change of velocity, measured in m/s². Acceleration occurs when speed or direction change

Forces and Free-Body Diagrams

• A force is a push or pull, having a size and direction, measured in Newtons (N).
• Net force is the combination of all forces acting on an object
• Balanced forces result in no change of motion
• Unbalanced forces result in acceleration

Newton's Laws of Motion

• 1st Law of Motion (Inertia): Objects in motion tend to stay in motion (or objects at rest stay at rest) unless acted upon by an unbalanced force
• 2nd Law of Motion: F = ma (Force equals mass times acceleration)
• 3rd Law of Motion: For every action, there is an equal and opposite reaction

Gravity and Work

• Mass and Weight: Mass is the amount of matter in an object; Weight is the measure of the gravitational force on an object
• Factors affecting gravity include mass and distance
• Objects accelerate towards Earth due to gravity at 9.8 m/s²
• Terminal velocity occurs when falling objects reach a constant speed, with resultant net force of 0N

Work & Mechanical Advantage

• Work is done when a force causes an object to move in the direction of that force, and measured in Joules (J)
• Work = Force x Distance
• Mechanical advantage is the ratio of the output force to the input force for a machine