Basic Physics 9, Quarter 4, Lesson 4: Magnetism

• Magnetism is covered in this lesson, which falls under Quarter 4, Lesson 4 of Basic Physics 9.

Introduction to Magnetism

• A magnet can be a rock or metal that pulls specific metals towards it.
• Magnetism is a basic force of nature, akin to electricity and gravity.
• Magnetism operates at a distance without physical contact.
• Magnets are common in everyday items such as refrigerator stickers, magnetic screws, caps, playboards, and pin holders.
• Cranes in industries and scrapyards use it to carry scrap metals.
• Magnetic compasses are used for navigation for centuries.

History of Magnets

• Magnetism's discovery is credited to Magnes, a Greek shepherd from Magnesia, Greece.
• Magnes noticed his stick's ferrule and his sandals' nails sticking to a rock while herding sheep.
• Iron was attracted to the magnetic rock.
• The stone was named magnetite, possibly after the shepherd or the region.
• Magnetite was also called a loadstone due to its attractive properties.
• Magnetite is a naturally occurring iron oxide.
• It can be magnetized to become a permanent magnet.
• Naturally magnetized magnetite pieces are called loadstone.
• Ancient Egyptians employed magnets in tricks, levitating objects of worship.
• A Chinese emperor used loadstone gates to fortify his palace.
• In 1820, Hans Christian Orsted discovered electromagnetism.
• Orsted noted a compass needle's deflection when an electric current was switched on/off.

Understanding Magnets

• A magnet attracts specific materials, like iron.
• Magnets have north and south magnetic poles.
• The poles are the strongest magnetic regions.
• Poles are named "north" and "south" due to their alignment with Earth's north-south axis when freely moving.

Magnetic Force and Fields

• Magnetic force is the force a magnet uses on materials or other magnets.
• This force operates over a distance, including attraction and repulsion.
• A magnetic field surrounds a magnet.
• Magnetic fields interact when magnets are close.
• Opposite poles attract, while like poles repel.

Magnetic Material Properties

• Magnetism is a material's ability to attract and act as a magnet.
• Electron movement in atoms causes magnetism.
• Electrons spinning around the nucleus make the atom a tiny magnet with poles and a field.
• Most materials do not exhibit magnetism due to atoms' poles pointing in all directions.
• Nonmagnetic examples include wood, glass, plastic, paper, copper, and aluminum.
• Magnetic domains are regions where atoms' poles align.
• The material is nonmagnetic in general because domains point in different directions.
• Materials become magnetized in a magnetic field.
• The magnetic domains align, magnetizing the material.
• Ferromagnetic materials like iron, cobalt, and nickel can be magnetized.

Temporary versus Permanent Magnets

• Materials can become temporary or permanent magnets once magnetized.

• Paper clips touching a magnet become temporarily magnetized.

• Removing the clips from the magnet's field causes the magnetic domains to misalign.

• Stroking an iron nail with a magnet creates a permanent magnet.

• The nail's magnetic domains remain aligned even removed from the field.

• Magnetite is a natural permanent magnet, also known as lodestone.

• Magnetite aligns with Earth's axis.

• Magnetite can attract small iron bits.

• A magnetite spoon compass was first used in China around 2000 years ago.

• The spoon's handle always points north.

Earth as a Magnet

• The lesson shifts to Earth's magnetism as Quarter 4, Lesson 2.
• Earth acts like a large bar magnet with magnetic poles along its axis.
• A magnetic pole is the magnet's end that exerts the most force.
• A compass needle points north, but not to Earth's geographic north.
• The geographic north pole is at 90° north latitude.
• The magnetic north pole is 80° north latitude.
• Earth has both geographic and magnetic south poles.
• Compasses point to the magnetic south pole, called the "north" magnetic pole due to its location near the geographic north pole.
• Earth's magnetic field protects the planet with solar winds.
• Earth's organisms are protected from radiation by the field.
• Navigation is benefited by the Earth's magnetic field.
• Compasses pinpoint the magnetic north for direction.
• Animals also use natural "compasses" to navigate.
• Loggerhead turtles navigate migration routes using magnetic fields.
• Migratory birds use magnetic fields to navigate.
• Recent research suggests birds can see Earth's magnetic field visually.