Page 100 - Physics_Form_2

Physics for Secondary Schools

Chapter Three

Magnetism

FOR ONLINE READING ONLY

Introduction

Knowledge of magnetism has provided several useful applications in daily life,
starting from the historical navigation by the Greeks to the present-day digital
world. In this chapter, you will learn the concept of magnetism and how materials
can be magnetised or demagnetised. You will also learn about magnetic fields,
including the Earth’s magnetic field. The competencies developed will enable you
to apply the knowledge of magnetism in various contexts.

Think
Life without the existence of magnetism

Concept of magnetism The lodestone tends to attract

Magnetism is a phenomenon produced by the certain metals more strongly
motion of electric charges that results in an at specific points on its surface
attractive and repulsive force between objects. than others. Any material that
The earliest observation of magnetism was has properties similar to those of
recorded in 600 BC by the Greek philosopher the lodestone is called a magnet.
Thales. He observed that pieces of iron were When magnets attract or repel
attracted to a natural mineral iron ore called each other, they exert a force
magnetite. The lodestone is an example of a called magnetic force. Magnetism
magnetised piece of the mineral magnetite. arises from two types of electron
Figure 3.1 shows an iron ore. motion as shown in Figure 3.2.
The first is the motion of electrons
around the nucleus of an atom.
The second type of motion is
the spin of electrons about their
axes. These motions of charged
particles independently impart a
magnetic effect, causing an atom

Figure 3.1: Iron ore to behave like a tiny magnet.

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Student’s Book Form Two

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