What is Compass: Definition and 87 Discussions

A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with magnetic north. Other methods may be used, including gyroscopes, magnetometers, and GPS receivers.
Compasses often show angles in degrees: north corresponds to 0°, and the angles increase clockwise, so east is 90°, south is 180°, and west is 270°. These numbers allow the compass to show azimuths or bearings which are commonly stated in degrees. If local variation between magnetic north and true north is known, then direction of magnetic north also gives direction of true north.
Among the Four Great Inventions, the magnetic compass was first invented as a device for divination as early as the Chinese Han Dynasty (since c. 206 BC), and later adopted for navigation by the Song Dynasty Chinese during the 11th century. The first usage of a compass recorded in Western Europe and the Islamic world occurred around 1190.

View More On Wikipedia.org
Recent contents Top users
  1. Z

    How Does a Nearby Power Line Affect Compass Accuracy?

    Homework Statement A surveyor is using a compass 8m below a power line in which a 100A steady current flows. The horizontal component of the Earth's magnetic field at the side is 0.38G. The compass' reading is : 1)0.025G 2)0.38G 3)0.1G 4)0.52G The Attempt at a Solution I...
  2. M

    Loop, compass and magnetic field

    Homework Statement A compass is placed in the middle of a metal loop with radius 0.10m. The compass points in the direction of the Earth magnetic field when the loop is at rest. When the loop revolves around an axis perpendicular to the Earth's surface with constant angular velocity, the...
  3. S

    Magnetic moment of compass needle?

    What would be a typical value of the magnetic moment of a compass needle (in SI units)? Thanks :-)
  4. O

    Rotational Inertia of compass needle

    Homework Statement A small compass needle is situated in a uniform magnetic field. When displaced from its stable equilibrium position through a small angle and then released, it oscillates with a frequency of 5 Hz. A millijoule of work is needed to twist the compass needle round through...
  5. H

    Why does a compass point to the north

    Homework Statement a compass always points to the north because a. the compass is a magnet with the pointer as the south seeking pole b. the compass is made of a magnetic material c. the compass is an electromagnet that is charged by rubbing when the needle is turning d. the compass is a...
  6. F

    Compass and Magnetic Susceptibility

    Hi all, I'm Luca from Italy. This is the technical setting. Assuming we have a compass/magnetometer placed on something of general shape and material. The magnetometer feels the Earth's magnetic field that we call H_earth: we know, however, that the field measured by the...
  7. J

    Q:Why is the direction designated by S22°30′E not commonly used in the US?

    The linked picture shows a compass rose showing the four cardinal directions, the four ordinal directions, plus eight further divisions. Picture: http://en.wikipedia.org/wiki/File:Brosen_windrose.svg south-southeast a compass point that is two points east of due south : S22°30′E [M-W...
  8. FeDeX_LaTeX

    What Happens When a Compass is Surrounded by North Poles?

    Hello; What happens if you took a compass and surrounded it completely with north poles (and no south poles)? Would the compass just spin repeatedly because it doesn't know what to point to? Also, the compass can't spin forever; so I'm guessing it will stop because the magnets can't last...
  9. C

    Current in a wire and compass needle

    Homework Statement A compass needle points 19.1 degrees E of N outdoors. However, when it is placed 9.80 cm to the east of a vertical wire inside a building, it points 55.7 degrees E of N. What is the magnitude of the current in the wire? The Earth's field there is 4.80×10-5 T and is...
  10. Q

    Dip Needle Compass vs. Normal Compass

    Why does one "dips" down and the other rotates?
  11. B

    Solve Suspended Compass Problem from Physics Olympiad

    Hi A friend of mine showed this problem he translated from a physics olympiad but I can't solve it: "Suspended compass Consider a perfectly symmetrical compass. It is constituted by two rigorously equal connecting rods, that join in a vertex the one that we call “pivot”. The opening angle...
  12. T

    Compass and straightedge angle construction

    Ok so couple questions, what is the use of this method of creating angles? does being able to construct an angle using only this method give that angle any special properties in physical situations, or is it just a matter of being a backup plan in case you for some reason happen to have a...
  13. Artlav

    Compass heading from cartesian vectors?

    Hello, How can i calculate compass heading from cartesian vectors? Specifically, a planet of radius R is located at (0,0,0), with north pole being at (0,R,0). An airplane is located at POS, and is flying in DIR direction. How can i determine the (true north) compass heading of the plane...
  14. A

    Tangent Galvanometer help (square loops around compass)

    What I had to do for a physics prac was to create a tangent galvanometer using this like...square piece of wood and a flat piece of wood in the middle... and we put a compass in the middle and increased the number of coils (carrying current) and recorded the deflection made by the compass and...
  15. U

    Effects of Placing a Compass Under a Cable

    Homework Statement If we put a compasd UNDER a cable.. Will that effect on the compass ? I WANT THE ANSWER AS SOON AS POSSIBLE Homework Equations The Attempt at a Solution
  16. P

    Is the Solar System Governed by a Compass Point Rule?

    I came across a site where a claim is made that the orbital periods and other such phenomena pertaining to the planets follow a compass point rule, ie. when translated to a compass type grid they adhere closely to the 8 main points of the compass, and that this only works when the periods etc...
  17. L

    Exploring Magnetic Compass Needles: An Unexpected Result!

    The topic of magnetic compass needles came up on another forum. This led me to get out some cheap compasses and start messing around with them. I lined up three compasses in a north-south row. I expected them to show magnetic north and they pretty much did. I also thought they would do about...
  18. T

    Compass in a solenoid, oscillating

    Homework Statement A compass, consisting of a small bar magnet resting on a frictionless pivot through its centre, is placed in the middle of a long solenoid, which in turn is aligned with its axis pointing North-South. With a current of 1 Amp passing through the solenoid, a small...
  19. M

    Calculating Electrostatic Force on a Charge in a Compass

    Homework Statement A charge of -4.10 C is fixed at the center of a compass. Two additional charges are fixed on the circle of the compass (radius = 0.137 m). The charges on the circle are -3.58 C at the position due north and +6.79 C at the position due east. What is (a) the magnitude and...
  20. rootX

    Find Your Political Compass - Test & Graphs | PoliticalCompass.org

    From http://www.politicalcompass.org/test I am Economic Left/Right: 3.12 Social Libertarian/Authoritarian: -3.49 There's aren't many people (as the result shows) in the fourth quadrant :shy: Uploaded Files: http://img53.imageshack.us/img53/5403/internationalchartco6.gif mine...
  21. K

    Straightedge and compass constructions

    1) Prove that 45 degrees can be trisected with straightedge and compass. My attempt: 60 deg constructible since equilateral triangle constructible and 45 deg constructible since 90 deg constructible and we can bisect any angle. =>(60-15)=15 deg constructible Then copy this angle 3...
  22. C

    Wire & Compass Homework: Effects of Distance & Series Batteries

    Homework Statement You are looking straight down on a magnetic compass that is lying flat on a table. A wire is stretched horizontally under the table, parallel to and a short distance below the compass needle. The wire is then connected to a battery so that a current flows through the...
  23. I

    Compass is installed on an iron ship

    when a compass is installed on an iron ship, why must there be small correcting magnets installed near the compass? Is it because the iron is itself magnetized somehow?
  24. R

    In what direction does a compass needle point?

    Homework Statement In what direction does a compass needle point? (More than one answer may be true.) T/F In the direction of the magnetic field lines at the location of the compass. T/F Toward the north magnetic pole if a bar magnet is brought near the compass. T/F Toward the south...
  25. ?

    Magnetic fields and a compass

    Plz help me if you can... Question: A compass needle is not always balanced parallel to the Earth's surface but one end may dip downward. explain. I know that the answer has something to do with the Earth's magnetic field...or may be even gravity. I've read in my physics textbook about the...
  26. P

    Why does the compass spin when a current passes?

    Could someone give a basic and concise explanation for it? Its surprising that textbooks talk about this example as how electricity and magnetism were first considered together but not explain why it was the case. Does the needle spin indefinitely? Or does it eventually point towards a...
  27. C

    Magnetic Compass Needle: Remanence & Airgap Effects on AC Performance

    1)does a magnetic compass needle have high remanence or low remanence? 2)in a shell type transformer core required to carry DC in addition to normal AC, what effect does the introduction of an airgap have on AC performance of such transformers.
  28. O

    How do animals & bacteria sense compass direction?

    You are probably aware of migratory behavior of birds. But what is the mechanism that accounts for this? It is based on a unique biochemistry that incorporates ferromagnetic material (magnetite) within them and utilizes their orientation to govern its spatial movement (horizontal and...
  29. A

    News Where Do You Fall on the Political Compass?

    Where do you fall? Near Stalin? Near Thatcher? Near Gandi? Near Bush? :-) http://www.politicalcompass.org/
  30. chroot

    How Does Latitude Affect the Compass Angle of Sunrise?

    A recent thread (https://www.physicsforums.com/showthread.php?t=69970) by DaveC426913 got me thinking about differential geometry. The compass angle at which the sun rises each morning varies with latitude, but not linearly; it actually seems to be a rather complicated relationship. Let's look...
  31. C

    How to Make a Non-Iron Compass

    How can you make a compass without using iron or other ferromagnetic material? At first, I thought to use a needle, but I was told that that was steel, and therefore iron. Any ideas?
  32. DaveC426913

    Sunrises and sunsets on the compass

    I feel a fool for even asking this; my father is a Geography teacher, and I am supposedly well-educated in the sciences. But the only dumb question is the one not asked, so... I've never quite understood where the Sun actually rises and sets on the compass. It does not set due West...
  33. S

    News Where are you on the political Compass

    www.politicalcompass.org click the "take the test" link at the bottom of the page and tell us where you are on the political compass! Economic Left/Right: -5.12 Social Libertarian/Authoritarian: -5.28 About the same spot as the Dalai Lama :rofl:
  34. I

    Is there a way of trisecting an angle using a compass, straight edge and pencil?

    I know that there is a way to bisect an angle using that equipment, but is there a way to trisect it. I have heard it is possible to do it by constructing a regular polygon with sides of a multiple of 3 around the angle. Does any1 have anything?
  35. C

    Understanding Focault's Compass - Gyroscope Rotation Dynamics

    Hi there, the Focault compass its supposed to be a fast spinning disk that keeps pointing to the Earth north the spinning axis is mounted on top of a rotating base, angle which is supposed to oscillate when slighty displaced from the north direction is this oscilatory behaviour...
  36. S

    Suppose you are navigating in Egypt deserts by trusting the compass

    Suppose you are navigating in Egypt deserts by trusting the compass to determine the South direction. If your destination is 15 km to the North of you, approximately by how much will you miss it?
  37. L

    News Where are you on the political compass?

    Take the test: http://www.politicalcompass.org/ Where do you stand? I am: Economic Left/Right: -1.75 Libertarian/Authoritarian: -5.13
Back
Top