موضوع انجليزي عن compass

موضوع انجليزي عن compass

معلومات عن البوصلة

معنى بوصة بالانجليزي

البوصلة المغناطيسية

كيف تعمل البوصلة

اسم مخترع البوصلة

مكونات البوصلة

البوصله لتحديد اتجاه القبله

اسم قديم للبوصله

معلومات عن البوصلة

اسم مخترع البوصلة

اجزاء البوصلة

انواع البوصلة

كيف تعمل البوصلة

لماذا البوصله تتجه الى الشمال

استخدام البوصلة

شرح البوصلة بالصور

اسم قديم للبوصله

A compass is a navigational instrument consisting of a magnetized needle that aligns with the magnetic field of the Earth. It thus indicates the Magnetic North, to be distinguished from the geographic North Pole. The difference between the two directions in a given place is called terrestrial magnetic declination. According to the required precision, this difference is accommodated or a compensation chart is used. Observed from France (in 2016), the two directions are essentially identical.

The lines of the Earth's magnetic field on which the compass needle aligns point underground at the north and south poles (not at the surface). In the northern hemisphere, the north end of the compass is drawn down. To compensate for this phenomenon, the southern end of the compass needle is lightly weighted.

When using a "northern hemisphere" compass in the southern hemisphere, the southern end of the needle is drawn down by the magnetic field, even though it already has a counterweight. Result, the southern tip of the compass hangs on the bottom of the cavity in which it is housed, and therefore works much less well.

A compass provides a known reference direction that aids navigation. The cardinal points are (clockwise): North, East, South, and West. A compass can be used in conjunction with a clock and a map to provide an estimate of its navigation.

In land navigation, the instrument used is usually called a compass. It consists of a needle that rotates in front of graduations of the instrument, usually held by hand, which is oriented in the desired direction. In marine and air navigation, or on a vehicle, a compass is preferably used: it is then the moving part that carries the graduations (sometimes in the opposite direction to those of a compass). It turns in front of a fixed marker parallel to the axis of the ship or the aircraft, called the line of faith, and gives directly the course followed.

Physical principle

A compass may consist of any device using a magnetized needle rotating freely on a pivot, so that it can indicate the direction of the magnetic north of the Earth.

The law of magnetism is such that opposite poles attract each other. By choice of historical convention, the North Pole of a magnet is the one that points North of the Earth. As a result, the magnetic pole of the Earth near the geographic North Pole (at the time of modern man) is a south pole in the sense of magnetism. This pole is however named "North Magnetic Pole" because it is more intuitive for a pole that gives approximately the geographic North.

In the past, some compasses were combined with a sundial, which used the shadow of a needle called style or gnomon or a folding triangle; this association made it possible to orient the dial and to obtain the time approximately (cf the astrolabe).

A gyroscopic compass can also be used to find geographic North.

The basic element is a magnetic rod. This can be achieved by aligning a steel rod on the Earth's magnetic field and then heating and cooling (annealing) or rubbing it. However, this method produces only a low power magnet; also other methods are preferable.

This magnetized rod (or magnetic needle) is then placed on a virtually zero friction support that allows it to rotate freely to align with the ambient magnetic field. A mark is then affixed at one end so that the user can distinguish the north and south directions. A modern convention is that the end pointing to the north is marked in some way, often with fluorescent or red paint.

Using the compass

Other features common to modern portable hand-held compasses are a baseplate with graduated rulers for measuring distances on maps, a rotating bezel for measuring the angle formed between magnetic north (see magnetic declination) indicated by the needle and the direction of the target point, and a mirror reflecting the image of the needle on the dial when targeting a landmark. Most compasses also have an aiming system consisting of a sight and a handlebar used as a collimator or a wire stretched in a recess, or a painted line or drawn in the cover. Some compasses have a magnetic needle supporting a mobile dial (such as the compass compass compass) and the reading is done automatically by means of a line of faith drawn on the glass (see the picture of the compass of the compass). US Army). A third type of compass, even more sophisticated, has a prism directed towards the outer edge of the dial and an eyepiece in which the angle value can be read directly (see photos).

The compass has several uses: navigation, artillery, geodesy etc. In navigation, it can be used to determine the current position of the user or indicate a procedure to follow.

• In the first case, the user must raise the location of points of reference (bridge, church steeple, mountain top, etc.) visible from the place where he is and compare his observations with a map. To this end, he will direct the sighting device of his compass towards the chosen marking point and then turn the telescope to put the mark indicating the magnetic north facing the direction indicated by the needle, visible in the mirror. The observer will then place the compass on the map (placed flat and oriented towards the magnetic north) and will locate the position of the previously marked point. To determine its position relative to this object, it will draw a straight line starting from the marking point passing through the center of the dial (point of rotation of the needle) and function of the measured angle. A second line starting from another visible point and cutting the first will determine the present position with more precision.