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Magnetism — KCSE Physics

KCSE Physics · 85 practice questions · 9 syllabus objectives · 9 revision lessons

28 easy29 medium28 hard

Last updated · Aligned to the KNEC KCSE syllabus

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Explain Earth’s magnetism, angle of dip, magnetic storage with keepers, and the repulsion test for polarity

State the properties of magnets and magnetic materials; describe magnetic field patterns around bar magnets and between poles

Explain the domain theory of magnetism and describe methods of magnetisation and demagnetisation

Distinguish between paramagnetic, diamagnetic and ferromagnetic materials and give examples of each

Identify magnetic and non-magnetic materials; distinguish ferromagnetic, paramagnetic and diamagnetic; state properties of magnets

Use the domain theory to explain magnetisation, demagnetisation and magnetic saturation

Describe methods of magnetisation (stroking, electrical, induction) and demagnetisation (heating, hammering, AC solenoid)

Define magnetic field, sketch field patterns for magnets, and describe field plotting using iron filings and compass

Magnetism

Revision Notes

Concise lesson notes for Magnetism, written to the KCSE Physics marking standard. Read the first lesson free below.

Understanding Earth's Magnetism

Earth's magnetism arises from its core, which consists of molten iron and nickel. This movement generates a magnetic field, similar to that of a bar magnet, with a north and south pole. The angle of dip, also known as the magnetic inclination, is the angle between the magnetic field lines and the horizontal plane. It varies depending on your location on Earth, being 90° at the poles and 0° at the equator.

Magnetic storage devices, like hard drives, utilize the principles of magnetism to store data. They often use keepers—pieces of soft iron that help maintain the magnetic field when the device is not in use, enhancing data stability and longevity.

The repulsion test for polarity is a method used to determine the poles of a magnet. When two magnets are brought close together, like poles repel each other while opposite poles attract. This can be observed by bringing a known north pole close to an unknown magnet; if they repel, the unknown is also a north pole.

Understanding these concepts is crucial in grasping how magnetism affects various technologies and natural phenomena.

Key points to remember

  • Earth's magnetism is due to its molten core movement.
  • The angle of dip varies from 90° at poles to 0° at equator.
  • Keepers are used in magnetic storage to stabilize data.
  • Repulsion test determines magnet polarity by observing interactions.

Worked example

Explain how the angle of dip varies across the Earth.

  • The angle of dip is 90° at the magnetic poles.
  • It decreases to 0° at the magnetic equator.

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More lessons in this topic

Lesson 2: Understanding Magnets and Magnetic Fields

Objective: State the properties of magnets and magnetic materials; describe magnetic field patterns around bar magnets and between poles

Magnets possess unique properties that distinguish them from non-magnetic materials. Key properties of magnets include:

  • Attraction and repulsion: Magnets attract ferromagnetic materials and repel like poles.
  • Polarity: Every magnet has a north and south pole; opposite poles attract, while like poles repel.
  • Magnetic field: Magnets create a magnetic field around them, which can be visualized using iron filings.

Magnetic Field Patterns: The magnetic field around a bar magnet can be illustrated through field lines. These lines:

  • Emanate from the north pole and terminate at the south pole.
  • Are denser near the poles, indicating a stronger magnetic field.
  • Form closed loops, showing that magnetic field lines do not start or end in space.

To visualize the magnetic field, sprinkle iron filings on paper above a bar magnet. The filings will align along the field lines, demonstrating the magnetic field pattern clearly.

  • Magnets attract and repel based on their poles.
  • Every magnet has a distinct north and south pole.
  • Magnetic field lines indicate the strength and direction of the field.
  • Field lines are denser near the poles of the magnet.
  • Magnetic field lines form closed loops.

Question: Describe the magnetic field pattern around a bar magnet. Answer: The magnetic field lines emanate from the north pole and curve around to the south pole. They are denser near the poles, indicating a stronger magnetic field.

Lesson 3: Understanding Magnetism: Domain Theory

Objective: Explain the domain theory of magnetism and describe methods of magnetisation and demagnetisation

The domain theory of magnetism explains how materials become magnets. According to this theory, all magnetic materials consist of small regions called domains. Each domain acts like a tiny magnet with a north and south pole. In an unmagnetized material, these domains are randomly oriented, resulting in no net magnetism. When a material is magnetized, the domains align in the same direction, producing a strong magnetic field.

Methods of magnetization include:

  • Using a magnet: Stroke a ferromagnetic material in one direction with a magnet.
  • Electric current: Pass an electric current through a coil wrapped around the material, creating a magnetic field.
  • Hammering: Strike a ferromagnetic material, which can cause domain alignment.

Methods of demagnetization include:

  • Heating: Expose the material to high temperatures, causing random domain orientation.
  • Hammering: Strike the magnetized material, disrupting domain alignment.
  • Alternating current: Pass an alternating current through the material, which causes domains to realign randomly.
  • Domains are small regions acting like tiny magnets.
  • Unmagnetized materials have randomly oriented domains.
  • Magnetization aligns domains; demagnetization disrupts them.
  • Methods include stroking, electric current, and heating.
  • Hammering can both magnetize and demagnetize materials.

Explain the domain theory of magnetism and describe one method of magnetization.

  • The domain theory states that materials consist of small regions called domains.
  • In unmagnetized materials, domains are randomly oriented.
  • A method of magnetization is stroking a magnet along the material in one direction.
Lesson 4: Types of Magnetic Materials

Objective: Distinguish between paramagnetic, diamagnetic and ferromagnetic materials and give examples of each

Magnetic materials can be classified into three categories: paramagnetic, diamagnetic, and ferromagnetic. Understanding these distinctions is crucial for your KCSE preparation.

  • Paramagnetic materials have unpaired electrons and are weakly attracted to magnetic fields. When exposed to a magnetic field, they align in the direction of the field but lose this property when the field is removed. Example: Aluminum and platinum.

  • Diamagnetic materials have all paired electrons, resulting in a weak repulsion from magnetic fields. They do not retain any magnetization once the external field is removed. Example: Copper and bismuth.

  • Ferromagnetic materials have unpaired electrons and exhibit strong attraction to magnetic fields. They can retain magnetization even after the external field is removed, making them useful in permanent magnets. Example: Iron and nickel.

Understanding these properties helps in identifying materials based on their magnetic behavior, which is essential in various applications, including electronics and engineering.

  • Paramagnetic materials are weakly attracted to magnets.
  • Diamagnetic materials are repelled by magnetic fields.
  • Ferromagnetic materials can retain magnetization.
  • Examples include aluminum (paramagnetic) and iron (ferromagnetic).
  • Magnetic properties depend on electron arrangements.

Distinguish between paramagnetic and diamagnetic materials, providing examples for each.

  • Paramagnetic materials have unpaired electrons; examples include aluminum and platinum.
  • Diamagnetic materials have all paired electrons; examples include copper and bismuth.

Sample Questions

Read 3 questions and answers free. Sign up to access all 85 questions with full KNEC-style marking schemes and a personalised study plan.

1
easySHORT ANSWER3 marks

List three methods of magnetisation and briefly describe each method. (3 marks)

Answer & marking scheme

Part (a) — 3 marks
Stroking: rubbing a magnet along a magnetic material in one direction aligns the domains (1 mk)
Electrical: passing an electric current through a coil wrapped around a magnetic material induces magnetism (1 mk)
Induction: placing a magnetic material in a magnetic field causes it to become magnetised without direct contact (1 mk)
2
easySHORT ANSWER4 marks

Identify and explain two ways in which the domain theory accounts for the process of magnetisation in ferromagnetic materials. (4 marks)

Answer & marking scheme

Part (a) — 4 marks
Domains align in the direction of the external magnetic field, increasing overall magnetisation (1 mk)
Increase in the number of aligned domains leads to stronger magnetic fields within the material (1 mk)
Domains can grow in size as more become aligned, enhancing the magnetic effect (1 mk)
The material retains magnetisation after the external field is removed due to domain alignment (1 mk)
3
easySHORT ANSWER4 marks

Identify and explain the differences between paramagnetic, diamagnetic, and ferromagnetic materials, providing one example of each. (4 marks)

Answer & marking scheme

Part (a) — 3 marks
Paramagnetic materials are weakly attracted to magnetic fields and do not retain magnetism; e.g. aluminium (1 mk)
Diamagnetic materials are weakly repelled by magnetic fields and also do not retain magnetism; e.g. copper (1 mk)
Ferromagnetic materials are strongly attracted to magnets and can retain magnetism; e.g. iron (1 mk)
Part (b) — 1 mark
Examples: Paramagnetic - aluminium, Diamagnetic - copper, Ferromagnetic - iron (1 mk)
4

Define the domain theory of magnetism and explain how a bar magnet can be magnetised. (4 marks)

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Frequently asked questions

What does the KCSE Physics topic "Magnetism" cover?

Magnetism covers Explain Earth’s magnetism, angle of dip, magnetic storage with keepers, and the repulsion test for polarity; State the properties of magnets and magnetic materials; describe magnetic field patterns around bar magnets and between poles; Explain the domain theory of magnetism and describe methods of magnetisation and demagnetisation, and more, all aligned to the official KNEC KCSE Physics syllabus.

How many practice questions are available for Magnetism?

HighMarks has 85 Magnetism practice questions for KCSE Physics, each with a full marking scheme. The first 3 are free; sign up to access the rest, plus all KCSE mock exams and past papers.

Are these aligned with the KNEC KCSE syllabus?

Yes. Every objective on this page is taken directly from the official KNEC KCSE Physics syllabus. Practice questions match the KCSE exam format and are graded against the standard KNEC marking scheme.

How should I revise Magnetism for the KCSE exam?

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Why Practise Magnetism?

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