أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٥_ p

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 5_ P


power(P)
puissance f

Ability. 1 - The rate of energy transfer or the rate of work. Its unit is the watt, which represents the transmission of one joule per second. The horsepower capacity is slightly less than 750 watts. Here are some useful equations for power:

Power (mechanical = force x speed = FV

Electrical power - potential difference x current = VI

(In alternating current circuits - in general - one must take into account that V and I may not be in phase.)

We often express efficiency as power, that is, the useful power output divided by total income. Thus, the yield in the case of the transformer is equal to P2/P1 = V2I2/V1I1

2 - Power measures how much a lens, mirror, or focusing system can focus a group of rays. High power means the ability to focus with the strength of its refracting unit, D dioptre.

P = 1/f


precision
precision f

Tightness. The number of significant figures in a given value. Thus, 1.234 meters is a more compact value than a length of 1.2 metres.

Accuracy is not the same as accuracy, as the latter measures how close a stated value is to the true value. Therefore, saying that a person's height is 1,234 meters is a precise but inaccurate measurement, while saying that his height is 1.8 meters is an accurate but less precise measurement.


pressure(p)
pression f

Pressure The force exerted on a unit surface of a material with which it is in contact. Therefore, to find pressure we use: pressure = force divided by area. The applied force is often the weight of an object, as in (a) below. Figure (b) shows two other cases. The unit of pressure is the pascal.
1 pascal = 1 newton/m2.

P₁ = F/A1

P2 = F/A2 > P1

p = W/A


The pressure at a depth in a liquid or in air is equal to the weight per unit area. Which gives the relationship:
Pressure = depth x average density x g.

See also air pressure manometer
And Archimedes principle.
Gas laws deal with pressure in gaseous samples.


pressure cooker
autoclave f

Pressure cooker. A device that cooks food quickly by bringing the water inside to a boil at a higher temperature than it would in an open pot. Since the vapor cannot escape, it raises the pressure, which raises the boiling point. It is common to obtain a pressure equal to twice the air pressure, so water boils at a temperature of approximately 120°C. Also called autoclave.


primary colours
coulours fpl fondamentales

Primary colours. See color vision.


prism binoculars
Jumelle f a prismes

Prismatic binoculars. A simple binocular has two telescopes mounted side by side. The use of high magnification (total internal reflection) gives prisms (see) and an upright (non-inverted) image without a significant increase in size. Also, the distance between the two objects is greater than the distance between the eyes of the observer, which improves binocular vision.


proportion
proportion f

suits. Two variable quantities x and y are proportional if for all values ​​y = kx, where » is a constant. We can write this as yax if the value is unknown. If yax, the graph of y with respect to x is a straight line passing through the origin (where 0=x and 0=y).

y = kx

And y is inversely proportional to x if the graph of y with respect to 1/x (or 1/y with respect to x) is a straight line through the origin.
Then the equation becomes: y=k/x. There are many physical laws that describe the proportionality between two measurements.
See, for example, gas laws and Hooke's law