plot the magnetic field lines of earth (without any magnet nearby) using a small compass needle.
Answers
The compass needle acts as a freely suspended magnet which points in north-south direction under the influence of earth's magnetic field lines. So, a small plotting compass can be used to plot a magnetic field.
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Explanation:
The method explained below shows the plotting of magnetic field lines with the help of a small compass needle:
Procedure:
1. With the help of some board pins, fix a sheet of paper on a drawing board.
2. At point 1 as seen in the below figure, place a small compass needle. From the top of the needle, mark two pencil dots at exactly two ends of the needle.
3. Move the needle to the compass to point 2 so that one end of the needle coincides with the second pencil dot.
4. The process of moving the compass needle to points 3, 4, 5… is continued in order to get a few dots.
5. When various dots are joined, a straight line is obtained.
6. Hence, one line of magnetic field of earth is traced.
Starting from a different point, the process is repeated and another line of magnetic field is traced out. This way a few several lines of magnetic field can be traced out. Every line is required to be labelled with the help of an arrow from the south pole of the needle towards the north pole to represent the direction of the magnetic field. The figure below depicts several magnetic lines that are obtained this way.