Power

power, in physics

power, in physics, time rate of doing work or of producing or expending energy. The unit of power based on the English units of measurement is the horsepower, devised for describing mechanical power by James Watt, who estimated that a horse can do 550 ft-lb of work per sec; a foot-pound is the work done when a weight (force) of 1 lb is moved through a distance of 1 ft. The unit of power in the metric system is the watt, named in honor of James Watt and equal to 1 joule per sec; the watt is used for measuring electric power in most countries, even those still using English units for other quantities. In common usage, the terms power and energy have become synonymous; for example, electrical energy is usually referred to as electric power (see power, electric). See also energy, sources of.

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power, in mathematics

power, in mathematics: see exponent.

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power

In science and engineering, the time rate of doing work or delivering energy. Power (P) can be expressed as the amount of work done (W), or energy transferred, divided by the time interval (t): P = W/t. A given amount of work can be done by a low-powered motor in a long time or by a high-powered motor in a short time. Units of power are those of work (or energy) per unit time, such as foot-pounds per minute, joules per second (called watts), or ergs per second. Power can also be expressed as the product of the force (F) applied to move an object and the speed (v) of the object in the direction of the force: P = Fv. See also horsepower.

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power

(1) Electricity. See current, volt, watt, AC and DC.

(2) The capability of a computer system. See computer power and throughput.

(3) (POWER) (Performance Optimization With Enhanced RISC) A RISC-based CPU architecture from IBM used in its Power Systems midrange computers and predecessors (for details, see Power Systems). POWER CPUs share a common instruction set with PowerPC CPUs, which were developed by IBM, Apple and Motorola (see PowerPC). Following is the evolution of POWER chips. See RISC.

                    Word  Number of    Number
  POWER     Year    Size  transistors  of
  Series    Intro. (bits) (millions)   Cores

  POWER7    2010     64     1200      4, 6, 8

  POWER6    2007     64      790      2

  POWER5    2004     64      276      2

  POWER4+   2002     64      180      2

  POWER4    2001     64      174      2

  POWER3-II 2000     64       23      1

  POWER3    1998     64       15      1

  POWER2    1993     32       15      1

  POWER1    1990     32        .8     1

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power

1. control or dominion or a position of control, dominion, or authority

2. a state or other political entity with political, industrial, or military strength

3. 

a. legal authority to act, esp in a specified capacity, for another

b. the document conferring such authority

4. Maths

a. the value of a number or quantity raised to some exponent

b. another name for exponent

5. Physics Engineering a measure of the rate of doing work expressed as the work done per unit time. It is measured in watts, horsepower, etc.

6. 

a. the rate at which electrical energy is fed into or taken from a device or system. It is expressed, in a direct-current circuit, as the product of current and voltage and, in an alternating-current circuit, as the product of the effective values of the current and voltage and the cosine of the phase angle between them. It is measured in watts

b. (as modifier): a power amplifier

7. 

a. mechanical energy as opposed to manual labour

b. (as modifier): a power mower

8. 

a. a measure of the ability of a lens or optical system to magnify an object, equal to the reciprocal of the focal length. It is measured in dioptres

b. another word for magnification

9. the sixth of the nine orders into which the angels are traditionally divided in medieval angelology

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power [′pau̇·ər]

(mathematics)

The value that is assigned to a mathematical expression and its exponent.

The power of a set is its cardinality.

For a point, with reference to a circle, the quantity (x-a)²+ (y-b)²-r², wherexandyare the coordinates of the point,aandbare the coordinates of the center of the circle, andris the radius of the circle.

For a point, with reference to a sphere, the quantity (x-a)²+ (y-b)²+ (z-c)²-r², wherex,y, andzare the coordinates of the point;a,b, andcare the coordinates of the center of the sphere; andris the radius of the sphere.

(optics)

focal power

(physics)

The time rate of doing work.

(statistics)

One minus the probability that a given test causes the acceptance of the null hypothesis when it is false due to the validity of an alternative hypothesis; this is the same as the probability of rejecting the null hypothesis by the test when the alternative is true.

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Power

The time rate of doing work. Like work, power is a scalar quantity, that is, a quantity which has magnitude but no direction. Some units often used for the measurement of power are the watt (1 joule of work per second) and the horsepower (550 foot-pounds of work per second). See Work

Power is a concept which can be used to describe the operation of any system or device in which a flow of energy occurs. In many problems of apparatus design, the power, rather than the total work to be done, determines the size of the component used. Any device can do a large amount of work by performing for a long time at a low rate of power, that is, by doing work slowly. However, if a large amount of work must be done rapidly, a high-power device is needed. High-power machines are usually larger, more complicated, and more expensive than equipment which need operate only at low power. A motor which must lift a certain weight will have to be larger and more powerful if it lifts the weight rapidly than if it raises it slowly. An electrical resistor must be large in size if it is to convert electrical energy into heat at a high rate without being damaged.

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power

The rate at which work is performed, energy is transformed or transferred, or energy is consumed; usually expressed in watts or horsepower.

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Power

Force, The

mystical source of a Jedi Knight’s righteous power. [Am. Cinema: Star Wars and sequels]

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POWER - Performance Optimization with Enhanced RISC. The IBM processor architecture on which PowerPC was based.

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Power 

a physical quantity measured as the ratio of work to the time interval during which the work is done. If the work is done at a uniform rate, power is defined by the formula N = A/t, where A is work done during the time t. In the general case N = dA/dt, where dA is the elementary work done during an elementary time interval dt (usually 1 sec). Power is measured in watts and sometimes (for engineering applications) in horse power.

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Power 

Originally, the term “power” in arithmetic and algebra meant the product of a specified number of equal factors. The product of n equal factors a is denoted by a”. Here, a is called the base, and n is called the exponent. In English, the term “power” is sometimes used in the sense of “exponent.”

The second power of a, written a², is also known as the square of a, or a squared. The third power of a, written a³, is known as the cube of a, or a cubed. It should be noted that a² is the area of a square with sides of length a and that a³ is the volume of a cube with edges of length a.

The fundamental operations on powers are given by the following formulas:

anm	= an+m
an ÷ am	= an–m
(an)m	= anm

The concept of power came to be extended to cases where the exponent is not a positive integer. Thus, if the exponent is zero, we have a⁰ = 1 when a ≠ 0. Negative exponents are also possible: a^–n = 1/aⁿ. For fractional exponents, we have (seeBINOMIAL EQUATION and EXTRACTION OF A ROOT). In the case of an irrational exponent α,

where r_n is an arbitrary sequence of rational numbers that approaches a. The rules of operations given above also hold for powers where the exponent is not a positive integer.

The theory of analytic functions deals with powers that have imaginary bases and exponents.