Heat and Waves

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# Heat and Waves - PowerPoint PPT Presentation

Heat and Waves. Chapter 10 and 12 Review. Agenda:. Waves. Hooke’s Law Amplitude, period and frequency Types of waves Wave speed Interference Standing waves. Heat. Temperature, measuring temperature, and thermal equilibriium Heat transfer is energy transfer

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### Heat and Waves

Chapter 10 and 12 Review

Agenda:

Waves

Hooke’s Law

Amplitude, period and frequency

Types of waves

Wave speed

Interference

Standing waves

Heat

• Temperature, measuring temperature, and thermal equilibriium
• Heat transfer is energy transfer
• Specific heat and calorimetry
• Latent heat
• Heat transfer
Temperature
• Temperature measures the average kinetic energy of the atoms or molecules of a substance.
• Temperature changes when energy is added or removed.
• All objects attempt to attain thermal equilibrium by exchanging energy.
Temperature Continued
• Matter expands as temperature increases. This is called thermal expansion.
• Temperature is measured in (see your formula sheet for coversions):
• degrees Fahrenheit
• degrees Celsius
• Kelvin
Heat
• Thermal energy is the measure of the TOTAL kinetic energy of the molecules of a substance
• Heat is the transfer of energy between substances.
• Substances at different temperatures will transfer energy until they are equal.
• Like all energy, heat can be measured in Joules.
Heat and Work
• Any energy change that cannot be accounted for by a change in potential or kinetic energy can be attributed to heat (internal energy) by way of friction.
Specific Heat
• Different materials require different amounts of energy to change their temperatures.
• The energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius is its specific heat capacity.
Calorimetry
• Specific heat capacity of substances can be determined by calorimetry.
• The amount of energy gained by the water must equal the amount of energy lost by the substance.
Energy during Phase Change
• It takes energy to change phases. TEMPERATURE DOES NOT CHANGE DURING PHASE CHANGE.
• Latent heat is the energy required to change phase.
• Problem solving: when determining the energy required to change a substance from one temperature to another, you must consider if there is a phase change or not.
Heat Transfer
• Conduction: heat transfer by direct contact between molecules
• Conductors allow the flow of heat easily
• Insulators inhibit the flow of heat.
• Convection: heat transfer through a fluid
• Radiation: energy transfer through electromagnetic waves.
Vibration and Waves:
• Hooke’s Law: the restoring force is proportional to the displacement of the object.
• Displaced objects have potential energy.
• Objects vibrate in simple harmonic motion if they behave according to Hooke’s Law (pendulums and mass-spring systems)
Measuring Simple Harmonic Motion
• Amplitude: the maximum displacement of the object
• Period: time for one complete cycle (Seconds)
• Frequency: how many cycles completed per second (Hz)
Pendulums and Mass-Spring Systems
• Period of a pendulum depends on pendulum length.
• Period of a mass spring system depends on mass and spring stiffness.
Wave Types
• Mechanical waves disturb a physical medium. Non-mechanical waves, like light, do not need a medium to travel through.
• Pulse waves are a single peak traveling. Periodic waves are repeated regular motions.
Waves Continued
• Transverse waves are perpendicular to wave motion.
• Longitudinal waves are parallel to wave motion
Wave Speed
• The speed of a wave is constant for any given medium.
• Frequency and wavelength are inversely proportional.
Interference
• When waves collide with each other, it is called interference.
• If the waves peaks are in the same direction, they add together for constructive interference.
• If the peaks are in opposite directions, they subtract for destructive interference.
Standing Waves
• Standing waves can be generated only at certain wavelengths relative to the length of the medium (L).
• 2L
• L
• (2/3)L
• (1/2)L
• (2/5)L
• etc.
Homework
• Finish study guide and check solutions.
• Review all slides, and get a good night’s sleep.