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24 Cards in this Set
- Front
- Back
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Heat
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In physics heat is energy in motion. Heat transfers energy within a body or from one body to the other when there is a temperature difference.
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How does heat move?
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Heat moves from higher temperature to lower temperature, lowering the former and raising the latter. Heat is measured in calories.
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Temperature
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Temperature measures how fast the molecules in a substance are moving. The faster the molecules move, the hotter the substance. Temperature is commonly measured on tow scales, Fahrenheit (freezing 32 degrees) boiling water 212 degrees and Celsius (freezing at 0 degrees and boiling water at 100 degrees. The Kelvin scale is used in science. Zero on the Kelvin scale is absolute zero-molecules are not moving at all and is equal to -273 degrees Celsius or -460 degrees Fahrenheit.
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How is heat transferred?
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Conduction (physical contact)
Convection (from moving liquid or gas) radiation (no physical contact) A heating pad conducts heat to your back. Moving hot water transfers heat to the radiator by convection. The sun radiates heat to earth. |
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Wave Phenomena
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Waves transfer energy without transferring matter. Microwaves, radio waves, sound waves, and x-rays are examples of waves in action (see example page 208). The frequency of a wave is the vibrations per second. The wavelength is the distance between crests.
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Light
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Most light is produced by heated electrons vibrating at high frequencies. Light makes it possible for us to see things and observe colors. Plants need it to carry out photosynthesis.
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How does light travel?
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In straight lines and spreads out as it travels. When light strikes a rough surface it may be absorbed or scattered. When light strikes a highly polished surface it is reflected away at the angle of the original ray (angle of incidence equals the angle of reflection). Black surfaces absorb all light, while white surfaces scatter all light. This is why light clothes are recommended for sunny days.
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Sound
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Sound are waves. For the human ear to hear a sound it must travel through a medium-a gas, solid, or liquid. As the sound waves travel through the medium, molecules in the medium vibrate. Sound travels more quickly through solid media because the molecules are more closely packed together.
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How fast does sound travel?
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Through the air about 1,100 feet per second, through water at about 5,000 feet per second, and through stone at about 20,000 feet per second.
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Electricity
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Like charges repel, unlike charges attract. Neutral charges are attracted by both positive and negative charges, but not as strongly as opposite charges
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How does electricity travel?
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It speeds through conductors such as copper. It moves slower though semiconductors such as ceramics. It does not move through nonconductors such as rubber and glass
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What are circuits?
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Electricity moves though wires to form circuits. Most circuits in this county use alternating current (AC). Circuits in other countries may use Direct current (DC)
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How are circuits wired?
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Most are parallel- if a light burns out or a switch is off, all other switches or lights work. Some are wired in a series and this means if a switch or light is out all of the lights go out.
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What units are used to measure electricity?
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As electricity moves through wires the volts measure the force of the current. The ampere (amp) measures the rate of current flow. The ohm tells the resistance in the wire to the flow of electricity.
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What are batteries for?
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They are used to produce, store, and release electricity. Batteries used in a toy or flashlight are dry cell batteries. Car batteries are wet cell batteries.
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Magnetism
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Magnets occur naturally in magnetite, although most magnets are manufactured from iron. Magnetism is very similar to electricity, and electromagnetic s can be made form coils of wire. Magnets have a north and south pole-like poles repel, while opposite poles attract. The magnetic field is strongest around the poles.
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How does magnetism relate to our earth?
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Earth has a magnetic field that aids in navigation. Magnetic north is located in northeastern Canada. It is not located at the North Pole. Compass needles point to magnetic north not to the geographic North Pole.
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Modern physics.
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study very small particles of energy. Energy as very small discrete quantities gives scientist a different view than energy as a continuous flow.
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Particle physics
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Is useful as scientist study atomic energy. For example, scientist study light as the transmission of tiny particles called photons. In fact, it is believed that energy is transmitted as both particles and waves.
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What is the conversion of matter into energy?
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Modern physics also studies this and energy into matter. Einstein's famous equation quantifies the conversion between mass to energy
E=mc squared E is energy, m is mass and c is speed of light, 186,000 miles per second. Calculations with this equation reveal that very small amounts of mass can create huge amounts of energy to create a very small amount of mass |
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Radioactivity
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Materials are radioactive when they have unstable nuclei. Uranium is an example of a naturally occurring radioactive substance. Radioactive materials decay, losing their radioactivity at a certain rate. The decay of radio active material is very useful for dating rocks and other materials.
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How are nuclear power plants related to radioactivity?
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Radioactive material is created through nuclear fusion at power plants. The energy from the reaction can be used as a power source. Radioactive materials release energy including alpha, beta, and usually gamma radiation. Gamma rays penetrate living organisms very deeply and can destroy living cells and lead to the death of humans
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Fusion
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The sun creates energy though fusion. Attempts are underway to create energy though nuclear fusion. Fusion creates much less radioactivity and could be fueled by deuterium, which is found in limitless quantities throughout the ocean.
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Interpreting graphs.
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page 212-213 make sure that you know how to interpret these graphs.
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