## Competency 044:Energy and Interactions between Matter and Energy

The teacher understands energy and interactions between matter and energy.

Energy, in a general sense, is the ability to do work. For more general information, read this article from the New Mexico Solar Energy Association, which examines the question, What are the different forms of energy?

### Work, Power and Potential and Kinetic Energy

The beginning teacher describes concepts of work, power, and potential and kinetic energy.

#### Key Concepts:

• Work is a measure of a force exerted over distance. The equation for work is w = force x distance.
• Power is the rate at which work is being done. The equation for power is p = work/time.
• Potential energy is the energy of a body due to its position or the arrangement of the particles of the system (such as a stretched spring).
• Kinetic energy is the energy possessed by an object due to its motion.

#### Resources:

The online Physics Classroom site provides a summary of work, energy, and power using practical examples and diagrams of these concepts and interactive questions.

### Heat Energy and the Difference between Heat and Temperature

The beginning teacher understands the concept of heat energy and the difference between heat and temperature.

#### Key Concepts:

• Heat is the energy that flows between objects because of a temperature difference between those objects. Heat flows spontaneously from an object or system of a higher temperature to an object or system of a lower temperature. Heat is measured in calories.
• Temperature is a measure of the average kinetic energy of the molecules in an object. Temperature is measured in degrees Celsius or Fahrenheit.

#### Resources:

The difference between heat and temperature is explained in an entertaining animated episode of the 1980 Canadian educational television series, Eureka.

Heat and Temperature are described in detail by the Thermal Physics lesson on heat and temperature from the Physics Classroom. Heat flow is described in a section on thermal equilibrium.

### Principles of Electricity and Magnetism and their Application

The beginning teacher understands the principles of electricity and magnetism, and their applications (e.g., electric circuits, motors, audio speakers, nerve impulses, lightning).

#### Key Concepts:

• Electricity and magnetism are related to each other and are combined as one of the four fundamental (universal) forces – electromagnetism.
• Electricity is a term that encompasses a variety of phenomena that result from presence and flow of an electric charge.
• Magnetism is a property of some materials that causes them to respond to an applied magnetic field.
• An electric field is the energetic region of space surrounding a charged object.
• A magnetic field is the region of space that interacts with a magnet. Usually, a magnetic field is located between the opposite poles of two magnets or in the space surrounding an electric current.
• Electric currents produce magnetic fields and moving magnetic fields produce an electric current. Many devices, such as electric motors, audio speakers, and computers, depend upon this interaction.

#### Resources:

Refer to Competency 41 for a description of the four fundamental forces.

The Physics Hypertextbook site features detailed information and graphics on the topic of electricity and magnetism in its chapter IV, Electricity & Magnetism.

The University of New South Wales offers a variety of animations and information on electric motors and generators, the right hand rule, and practical applications such as loudspeakers. The animations include graphs showing current variations of mechanical devices.

PHYSICS4KIDS provides a concise overview of electricity and magnetism, including electric fields, current and AC or DC power.

### Properties of Light

The beginning teacher applies knowledge of properties of light (e.g., reflection, refraction, dispersion) to describe the function of optical systems and phenomena (e.g., camera, microscope, rainbow, eye.)

#### Key Concepts:

• Light is a general term that encompasses a wide range of frequencies, wavelengths, and energies from radio waves to cosmic radiation.
• The electromagnetic spectrum is a graphic organizer that arranges the major kinds of radiation according to their wavelengths. Visible light, the light humans see, is a narrow part of the electromagnetic spectrum ranging in wavelengths from about 380 (violet) to 750 (red) nanometers.
• Light is emitted in tiny energy packets called photons and exhibits properties of both particles and waves.
• Light travels through a vacuum at a speed of 299,792,458 meters per second. The speed of light is reduced when it travels through various transparent materials, such as water, air, and glass. The ratio by which light is slowed by transparent materials is called the refractive index.
• Light can be made to reflect off various surfaces such as mirrors or water.
• Light rays will refract (bend) when passing through transparent materials if the angle of incidence of less than 90 degrees.
• Visible light, a combination of red, orange, yellow, green, blue, indigo, and violet, will disperse when passing through a triangular prism or through water droplets (rainbow). Each of the visible colors refracts a different amount depending upon its wavelength and this produces dispersion. Visible colors correspond to different wavelengths of light as perceived by the eye and brain.
• Ray diagrams, representing the direction of travel for light waves, are used to show the path of light as it reflects off a mirror or refracts and disperses as it passes through a transparent material.

#### Resources:

View this diagram to see the electromagnetic spectrum with references to radiation type and wavelength, and recognizable objects for scale, frequency, and temperature.

NASA’s Space Based Astronomy Educator Guide (grades 5-8) features a chapter on the electromagnetic spectrum. The chapter includes EM activities.

Michael Fowler of the University of Virginia Physics Department describes the history and science behind determining the speed of light in this short lecture manuscript.

Professor Walter Lewin explains reflection, refraction, and dispersion in this video lecture from the Massachusetts Institute of Technology’s OpenCourseware site.

Lenses and Mirrors is the topic of this background essay from the Physics Department at Duke University. The science and mathematics behind the function of lenses and mirrors (refraction and reflection) are explained with text, diagrams, and equations.

### Properties, Production and Transmission of Sound

The beginning teacher demonstrates an understanding of the properties, production, and transmission of sound.

#### Key Concepts:

• Sound is a vibration that travels through objects and materials. The greater the density of a medium, the greater the speed of the sound waves that travel through the medium.
• Sound cannot travel through a vacuum.
• Sound travels in waves and the waves have characteristics such as wavelength, frequency, and amplitude. The frequency of a sound wave determines the pitch perceived by a human. The higher the frequency of a sound wave, the higher the pitch.

#### Resources:

The Nature of a Sound Wave is a three-part lesson on the science of sound from The Physics Classroom. The lesson features text and animations that show how sound is a wave phenomena.

The Physics Hypertextbook discusses the nature of sound and provides tables showing the speed of sound through various materials and frequencies of sound sources.

The University of Colorado at Boulder Interactive Simulations lab (PhET) has created interactive simulations on sound waves. “Sound,” Wave on a String, and “Fourier: Making waves” illustrate principles of sound waves.

### Properties and Characteristics of Waves

The beginning teacher applies knowledge of properties and characteristics of waves (e.g. wavelength, frequency, interference) to describe a variety of waves (e.g., water, electromagnetic, sound).

#### Key Concepts:

• A wave is a disturbance that travels through space and time with no actual transport of matter. A wave is a vibration such as sound, light, or a mass movement in the Earth’s crust that sends vibrations through Earth and across its surface (earthquake).
• Waves are measured by their frequency, wavelength, and energy. Frequency is the number of waves passing a point in one second. Wavelength is the distance between similar points on two successive waves. The speed of a wave through the material determines its wavelength.
• The amplitude of a sound wave is a measure of the magnitude of change in the oscillation of the wave.
• Only electromagnetic waves are able to pass through a vacuum. Sound waves, water waves, and earthquake waves require a material to pass through.
• Wave interference takes place when waves from different sources superimpose to form a resultant wave of greater or lesser amplitude. Waves with opposite phases can cancel each other.

#### Resources:

The Office of Naval Research has produced a Science and Technology Focus on ocean waves that explains their properties and dynamics.

Regents Physics at APlusPhysics features a discussion on “Wave Characteristics.” The site has animations and an entertaining video of how sound waves are able to shatter a wine glass. (Note: Safety procedures are somewhat lacking.)

The University of Colorado at Boulder Interactive Simulations lab (PhET) has created interactive simulations on sound waves. “Wave Interference” shows how waves add and subtract energy from each other.