How A Compass Works

Inside the earth is a big ball of Iron, which produces a magnetic field. The lines of the magnetic field all point in one direction, as shown on the diagram.

Inside a compass is a small magnet attached to a needle. I am sure you remember that magnets attract each other and in the case of the compass, the magnet of the needle will be attracted to the Magnet produced by the Earth.
Since the magnetic lines always point in one direction, the compass needle will also point in one direction. Thus we can know where the North pole is.

Since a compass is affected by magnetic fields, it needs to be used away from such items as iron and steel objects. These include: pocket knives and railway tracks

Parts Of A Compass

There are several kinds of campasses, however I will only show the parts on one type, the Silva Compass. The Silva Compass has a base plate and this is most suitable for orienteering.
Magnetic Needle. This always point to the magnetic North Pole.
Compass Housing. This can be turned from the base of the unit. On the housing will be marked the letters N, S, E and W for North, South, East and West. Also but not shown on the drawing will be numbers. This is a scale from 0 to 360 and represents the degrees around a circle.
Orienting Arrow. This is really part of the housing and turns with the housing. Along with the lines of the base of the compass they enable you to to 'set' a map, but more of that later.
Magnifying glass. Hope you know how to use that.
Travel arrow. If you set a bearing, then once aligned this arrow says which way to walk.
Scales. In the above picture the scales are shown on the front of the compass, however there are often more scales down the sides and these enable you to take measurements from maps of the distance between two points. As you will see when we get to using a map and compass together, we can measure the distance between to places on the map and using the scale, work out how far between those points.

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