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

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


refrigeration
refrigeration f

cooling. Technology to transfer energy from a cold box to the hotter outside air. Since this is not a natural trend for net energy transfer, a motor must be used. The engine pumps a special fluid in a closed loop. The pump raises the pressure of the fluid, making it liquid and releasing latent heat. At this point, the liquid goes through the black radioactive coil to the outside. It is forced through the valve to the low-pressure side of the loop, causing it to evaporate. This process cools the matter and its surroundings.


regelation
registration f

Refreezing. Ice has a rare property, which is to melt if the pressure on it increases. Refreezing is the process that occurs when the pressure drops again. The snowball and tiny ice crystals partially melt when compressed. Returning to freezing after the pressure is removed makes the ball hold together stably.


relative density
Densité f relative

Relative density. See density.


relativity
related f

Relativity. A theory that describes matter, space, and time and how they are interconnected. See Einstein. The special theory (1905) says that all the laws of physics remain the same for all people who move at a constant speed relative to each other. In particular, they find the same value for the speed of light, about (3 x 108 meters per second).

The theory says, among other things, that the speed of time, mass, and length of a moving object all depend on its perceived speed. Also: It is not possible to force any body to move at the speed of sound, or at a faster speed. This is followed by the famous equation W=mc2. In fact, it means that mass and energy are equivalent. No experience has given reason to doubt these concepts, which are, in fact, part of daily research in many fields. The general theory of relativity (1915) is mainly concerned with gavity. It says that light bends near an object with a large mass and that its wavelength changes as well. Once again, we say that experiments support these statements. Since the emergence of the two theories, many have been trying to disprove them without achieving any success. In fact, some aspects are still not completely clear. On the other hand, many attempts have been made to make relativity part of more modern and broader theories. But these attempts were not successful.


relay
relative m

deported. A device based on an electromagnet allows a small current to control a large one. When the small coil current appears, the core attracts the plate towards it and the main circuit breaker closes. A small interruption in the current leads to the opening of the main circuit.


resistance(R)
resistance f

resistance . The opposition of an element or section of a circuit to the flow of charge (current). Its unit is “ohm”, which is the opposition of a sample that passes one ampere when the voltage 7 between the two terminals is equal to one volt. See Ohm's law. We can measure the resistance R using the formula R=V/I using an ohm meter, a voltage divider, or a circuit like the one shown below.

All components of a normal circuit have resistance. By opposing the current, there is an energy transfer that raises the temperature (see fuse). The power involved is equal to the rate of power transmission, i.e. VI, V2R, or I2R. Temperature often affects the resistance of a sample. In the case of most metals, an increase in temperature leads to an increase in resistance, but in the case of semiconductors and insulators, the resistance decreases.