Magnets: Attract, Repel, and Magnetic Poles - Second Grade Science
Magnets are among the most fascinating objects in the physical world. A magnet can reach out through empty air, glass, and water to pull an iron paperclip toward itself without even touching it! Magnets hold drawings firmly on your kitchen refrigerator door, guide hikers through dense forests using magnetic compasses, and power electric motors that spin fans and electric cars. Understanding magnetism reveals the invisible magnetic force fields that surround magnets and our entire home planet.
What is a Magnet?
A magnet is an object or material that produces an invisible magnetic field, which exerts a force of attraction or repulsion on magnetic materials.
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| MAGNETIC VS. NON-MAGNETIC MATERIALS |
| |
| MAGNETIC (Attracted to Magnets) NON-MAGNETIC (Ignored) |
| - Iron and Steel nails/screws - Wood and Paper |
| - Nickel coins - Plastic and Glass |
| - Cobalt alloys - Aluminum foil and Copper |
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What Metals Are Attracted to Magnets?
A common mistake is thinking that magnets attract all metals. This is false! Magnets only attract a few specific ferromagnetic metals: iron, steel (which contains iron), nickel, and cobalt. Common metals like aluminum soda cans, copper pennies, gold jewelry, and silver silverware are NOT magnetic!
The Two Magnetic Poles: North and South
Every magnet, no matter its shape or size, has two ends called magnetic poles. One end is the North pole (N) and the other is the South pole (S). The magnetic force is concentrated with the greatest strength at these two poles.
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| ANATOMY OF A BAR MAGNET |
| |
| [ NORTH POLE ] [ SOUTH POLE ] |
| +------------+---------------+------------+ |
| | N | | S | |
| +------------+---------------+------------+ |
| Strongest Force Strongest Force |
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The Fundamental Rule of Magnetism
When you bring two magnets near each other, they will either leap together or push each other away with surprising strength. Their behavior follows an absolute rule of physics: Opposite poles attract, and like poles repel.
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| THE LAW OF MAGNETIC ATTRACTION |
| |
| OPPOSITE POLES ATTRACT (Pull Together!) |
| [ N ] ========> <======== [ S ] |
| North and South pull tightly toward each other! |
| |
| LIKE POLES REPEL (Push Apart!) |
| [ N ] <======== ========> [ N ] OR [ S ] <======== ========> [ S|
| North pushes North away! South pushes South away! |
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Attract: Jumping Together
When you place the North pole of one magnet near the South pole of another, invisible lines of magnetic force pull the two poles together with a snap.
Repel: The Invisible Wall
When you try to push two North poles together (or two South poles together), you will feel a firm, rubbery resistance like an invisible bouncy wall pushing your hands apart. No matter how hard you push, they will try to twist away from each other.
The Invisible Magnetic Field
A magnet does not have to touch an object to act on it because every magnet is surrounded by an invisible zone of magnetic influence called a magnetic field.
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| MAPPING A MAGNETIC FIELD |
| |
| ( ( ( ( ( ( ( ( | ) ) ) ) ) ) ) ) |
| / \ |
| v v |
| [ N ] =============================== [ S ] |
| ^ ^ |
| \ / |
| ( ( ( ( ( ( ( ( | ) ) ) ) ) ) ) ) |
| |
| Magnetic field lines flow OUT of North and loop INTO South! |
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Iron Filings Demonstration
If you place a sheet of paper over a bar magnet and sprinkle fine iron filings on top, the tiny metal slivers align along the invisible magnetic field lines, forming beautiful curved loops that flow from the North pole to the South pole.
Earth is a Giant Magnet!
Planet Earth behaves like an immense spherical magnet with its own global magnetic field!
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| EARTH'S GLOBAL MAGNETIC FIELD |
| |
| Geographic North Pole |
| ( N ) |
| / \ |
| | [M] | Molten iron outer core creates |
| | A G | Earth's magnetic field! |
| \ / |
| ( S ) |
| Geographic South Pole |
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The Earth's Molten Iron Core
Deep inside Earth, churning currents of liquid molten iron in the outer core generate a powerful planetary magnetic field. This magnetic shield deflects dangerous solar radiation from the Sun, making life on Earth possible.
How a Magnetic Compass Works
A navigation compass contains a lightweight magnetized steel needle balanced on a frictionless pivot pin. Because opposite poles attract, the north-seeking pole of the compass needle aligns with Earth's magnetic field lines, always pointing toward magnetic North, allowing travelers to navigate safely.
Chapter Review Exercises
Question 1: What is the fundamental rule of magnetism regarding how like poles and opposite poles interact?
Question 2: Which of the following objects will be attracted to a magnet, and why: a steel paperclip, a wooden block, a copper penny, and an iron nail?
Question 3: What is a magnetic field, and how can scientists make this invisible field visible using iron filings?
Question 4: Why does a magnetized compass needle always point toward the North Pole of the Earth?
Solutions and Explanations
Solution 1: The fundamental rule of magnetism is that opposite poles attract (North attracts South) and like poles repel (North pushes North away, and South pushes South away).
Solution 2: The steel paperclip and the iron nail will be attracted to the magnet because both contain iron, which is a ferromagnetic metal. The wooden block and the copper penny will not be attracted because wood and copper are non-magnetic materials.
Solution 3: A magnetic field is the invisible area of magnetic force surrounding a magnet. Scientists make it visible by placing a sheet of paper over the magnet and sprinkling iron filings on top; the metal filings act like miniature compasses, lining up along the curved magnetic field lines.
Solution 4: Earth contains a churning molten iron core that turns our planet into a giant magnet with magnetic poles. The compass needle is a tiny magnet that rotates freely, and its north-seeking pole aligns with Earth's natural magnetic field lines to point toward the North Pole.