Magnets and Magnetic Fields

Question 1

What are natural and artificial magnets?

Answer 1

Natural Magnets: Occur naturally in nature, such as lodestone, which is a naturally magnetized piece of the mineral magnetite.
Artificial Magnets: Man-made magnets, created by magnetizing materials like iron or steel.

Question 2

What are the magnetic properties of soft iron and steel?

Answer 2

• Soft Iron: Easily magnetized and demagnetized; used in electromagnets and transformer cores due to its high magnetic permeability.
• Steel: Retains magnetism for a long time; used for permanent magnets because it has high coercivity.

Question 3

What are the methods of making magnets?

Answer 3

• By Contact: Rubbing a magnetic material with a magnet.
• By Induction: Placing a material in a strong magnetic field, which magnetizes it.
• By Electric Current: Passing an electric current through a coil wound around a material to induce magnetism (electromagnetism).

Question 4

What is a magnetic field?

Answer 4

The region around a magnet where magnetic forces can be felt. The strength and direction of the magnetic field can be represented by field lines.

Question 4

What are the methods of demagnetizing magnets?

Answer 4

• Heating: Heating a magnet above its Curie point.
• Hammering: Striking a magnet while it is demagnetized or at a high temperature.
• Using Alternating Current: Exposing a magnet to an alternating magnetic field.

Question 5

What is the magnetic field of a permanent magnet?

Answer 5

A permanent magnet creates a magnetic field that is continuous and emanates from its north pole and enters through its south pole, forming closed loops.

Question 6

What are the properties of the Earth’s magnetic field?

Answer 6

• North and South Poles: The geographic north and south poles where the magnetic field lines converge.
• Magnetic Meridian: A line connecting the magnetic north and south poles.
• Angle of Dip: The angle made by the Earth’s magnetic field with the horizontal plane, which varies by location.
• Angle of Declination: The angle between geographic north and the magnetic north.

Question 7

What is magnetic flux and flux density?

Answer 7

• Magnetic Flux (Φ): The total magnetic field passing through a surface area.
  Formula: Φ = 𝐵 × 𝐴 × cos ⁡(𝜃)
  where 𝐵 is the magnetic field strength, 𝐴 is the area, and
  𝜃 is the angle between the field and the normal to the surface.
• Magnetic Flux Density (B): The amount of flux per unit area.
  Formula: 𝐵 = Φ / 𝐴
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