أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ١_ p

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 1_ P


parallax
parallaxe m

Parallax. The apparently different relationships between objects located at different distances when viewed from different locations. Thus, trees viewed from a moving train appear to be displaced relative to distant hills. There is no difference in view between two objects located at the same distance.


parallel circuits
Circuits in parallel

Parallel circuits. Electrical components connected in a circuit so that current is distributed between them. The voltage between the ends of each component is the same. There are three transistors in parallel in (a) below.

The resistance R of the set is given by this equation:
1/R = 1/R1 + 1/R2 + 1/R3

Figure (b) shows three parallel capacitors, the sum of their capacitances is:

C = C1+C2 + C3

( a )

I = I1 = I2 = I3

VIR = VIR₁+ V/R2 + V/R3

.1/R1 = 1/R1 + 1/R2 + 1/R3

( B )

Q = Q1 + Q2 + Q3

QQ₁+ Q2 + Q3

VC = VC1 + VC2 + VC3

C = C1+ C2 + C3

Compare with series circuits.


parallel forces
forces fpl parallèles

Parallel forces. See equilibrium and couple.


parallelogram rule of vectors
Please click on the visual parameter

Parallelogram rule for vectors. We use this rule to find the unary vector (resultant) that has the same effect as two. In (a) below we see two tug boats pulling a ship with its engine stopped. The two forces exerted on the ship are like the tension in the two cables. The ship can only move in one direction, not two. In fact, one force acted on it, which is the resultant of the two tensions (b).

Here we list the steps we follow when using the parallelogram rule:

a) Choose the scale. It is in the figure below 1 mm each
2 kilonewtons.

b) Draw the two forces to scale, making the right angle at the common point.

c) Complete the parallelogram (the two dashed lines).

The resultant force is 50 kN at a direction angle of 036°.

d) Draw the diameter from the starting point (line
dotted).

e) Use the scale to find the value of the resultant. Notice its direction as well.

Thus, the ship is moving at a direction angle of 036°. If its mass is 10,000 tons, it will accelerate by 5 mm/s2.
(See Newton's laws of motion).