أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٢_ p

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 2_ P


particle. particle
particule f

particle. In physics, it is a very small body. We describe the structure of matter through particles. See kinetic model. In very simple forms of matter, such particles are called atoms or molecules.

In an ordinary atom, there are three types of particles that differ in mass and charge. We use nuclear standards in the table showing the values ​​of these types below. The atomic mass unit is about 1.7 x 27-10 kilograms, and the “atomic charge unit” is about 1.6 x 19-10 coulombs.

Particle -- mass -- charge -- location in an atom
Electron ---- 1- --- 0 --- Cloud
Proton ---- 1+ ---- 1 --- Nucleus
Neutron --- 0 ---- 1 ---- Nucleus

It is clear in modern thought that particles can sometimes appear in the form of waves. In other words, particles can exhibit wave properties, such as diffraction and interference. Thus, the electron microscope cannot be understood except by thinking of the electron beam as a radiation wave.

On the other hand, quantum theory says that, in some cases, we have to think of waves as particles. We cannot fully explain photo-electric effects unless we do so. Particles of wave radiation are called quanta. In the case of electromagnetic waves, we call them “photons.”


pascal
pascal m

Pascal. Pressure unit.


pendulum
pendulum m

Pendulum A body that oscillates regularly and moves regularly, back and forth, between kinetic and potential energy. The T period depends only on the length and acceleration of free fall.
All the mass of the simple pendulum is, in fact, in the spherical weight at the bottom of the pendulum. People use this by mass to find and, and the equation is:

g = 4π2I/T²


period(T)
period f

turn . The time of a complete cycle of a repetitive movement (periodic or harmonic), such as the Earth’s rotation around the sun, the swing of a pendulum, the movement of an engine piston, and the vibration of a guitar or oud string. The unit of the cycle is the second, s. The cycle of motion is equal to the reciprocal of its frequency. When movement is shown in the form of a graph of displacement with respect to time, it is:
The cycle T is as shown in the figure below. See wave.


periscope
periscope m

Sorry. An optical instrument used to give an image of an object that would not have been seen without this instrument. For the simple projection in (a) below, there are two mirrors placed in a tube. Prisms, as in (b), give better results but are more expensive. See -total in internal reflection. Lenses may be added for magnification.


permanent magnet
Aimant m permanent

Permanent magnet. See magnetic material.