| Glossary | ||||||||||||||
| kinetic theory
— theory of matter that uses statistical mechanics to derive observable macroscopic properties, such as temperature and pressure, from the microscopic behavior of collections of particles. Kirchhoff’s current law — sum of all currents entering a junction must equal the sum of all currents exiting that junction. Kirchhoff’s voltage law — sum of the voltage drops (voltage differences) around a closed loop equals zero. laser — scientific instrument that produces a beam of coherent light, i.e., that has the same frequency, direction, and phase. Acronym for light amplification by stimulated emission of radiation. law of conservation of energy — total energy in a closed system does not change over time. While energy cannot be created or destroyed, it can be transformed from one form to another, just as long as the total energy remains constant. law of conservation of momentum — total momentum of a system is constant in the absence of outside forces acting on the system. law of reflection — when a light ray reflects off a surface or boundary between two materials, the angle of reflection is equal to the angle of incidence. law of universal gravitation — force of attraction between two objects is directly proportional to each of their masses and inversely proportional to the distance between them. length — separation between two points. A fundamental measure of space with common units of meters, feet, and miles. lens — transparent optical device that refracts light and is shaped in such a way either to converge or diverge light rays to focus them into an image. Lenz’s law — direction of the current induced in a wire is such that the current’s induced magnetic field opposes the change in magnetic field that originally induced the current. lever — elongated, rigid object that may rotate around a point (the fulcrum) under the action of one or more forces. The lever is one of six kinds of simple machines. | lever arm
— perpendicular distance from the center of rotation to the line of action of a force. light — form of radiant energy consisting of electromagnetic waves traveling at the speed of light. line of action — imaginary line that passes through a point and follows the direction a force acts. line spectrum — distinct pattern of emission or absorption spectral lines, each line corresponding to a unique wavelength of light, coming from a material when viewed in a spectrograph. linear momentum — momentum due to an object’s motion in a straight line, which is the product of mass and velocity. Also called momentum. Linear momentum has units of kg m/s. liquid — phase of matter that maintains its fixed volume, flows to take the shape of its container, and contains particles with intermolecular bonds that are continually being broken and reformed. longitudinal — type of wave where the oscillations are along the direction of motion of the wave itself. lubrication — technology of using fluids such as oil or other materials to reduce friction. machine — device that changes the magnitude and/or direction of a force. A machine is a mechanical system that is capable of doing work. macroscopic — scale that is large enough to be directly sensed, such as the scale of things in the everyday world. magnetic — property of a material that describes its ability to exert a force on a magnet or a magnetic material. magnetic domains — region of a material comprised of many atoms with their individual magnetic fields aligned. By having their magnetic fields aligned they add together rather than cancel each other out. magnetic field — force field surrounding magnetic objects. Measured in units of teslas (T). magnetic field lines — the arrows that depict the direction of the magnetic force in a magnetic field. Magnetic field lines are drawn with arrows pointing away from magnetic north pole and towards magnetic south pole. | |||||||||||||
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