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The Earth behaves like a giant bar magnet and as such there is a magnetic field present around it. The Earth’s magnetic field is thought to be caused by flowing liquid metals in the outer core of the planet which causes electric currents and a magnetic field.

Video 1: What are frequency polygons?
Video 2: Examples of frequency polygons
Video 3: Further examples of frequency polygons

By the end of this unit you will be able to:

• Calculate measures of central tendency and percentiles on grouped data.
• Construct a frequency polygon.
• Construct a line graph.

Introduction to magnetism: Wikipedia article that provides an overview of the concept.

The force that acts across the air gaps between magnets is the same force that creates wonders such as the Aurora Borealis. In fact, magnetic effects pervade our lives in myriad ways, from electric motors to medical imaging and computer memory. In this chapter, we introduce magnets and learn how they work and how magnetic fields and electric currents interact.