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Introduction to Magnets
Reshma’s Story:
Reshma’s Story:
- Reshma, from Kerala, loves writing stories.
- She wrote a story about sailors in the olden days who used stars to navigate.
- During a storm, with an overcast sky, stars weren’t visible, so Reshma couldn’t continue her story.
- She discovered that sailors used a magnetic compass to find directions.
What Are Magnets?
- A magnet is a material or object that produces a magnetic field. This field attracts certain metals like iron, nickel, and cobalt.
- Types of Magnets –
- Natural magnets: Found in nature, such as lodestones. Ancient sailors used lodestones to navigate.
- Artificial magnets: Man-made magnets, made from different materials, found in everyday objects, like those in pencil boxes and toys.
Magnetic and Non-Magnetic Materials
Activity 4.1: Exploring Materials
- Objective: Test which materials are magnetic.
- Steps:
- Collect objects made of different materials (e.g., iron nail, plastic spoon).
- Predict which ones will stick to a magnet.
- Test with a magnet and observe.
- Record findings.
- Results:
- Some materials stick to the magnet, some don’t.
- Magnetic materials: Materials that are attracted to magnets (e.g., iron, nickel, cobalt).
- Non-magnetic materials: Materials that do not get attracted to magnets (e.g., plastic, wood).
Poles of a Magnet
Activity 4.2: Investigating Poles
- Objective: Discover the poles of a magnet.
- Steps:
- Spread iron filings on paper.
- Place a bar magnet over them.
- Observe how iron filings stick to the magnet.
- Results:
- Poles: Most filings stick at the ends of the magnet (North and South poles).
Magnetic Poles– The two ends of a magnet where the magnetic force is the strongest. One end is the North pole, and the other is the South pole.
Poles: Magnets might have poles marked as N (North) and S (South). Sometimes the North pole has a white dot or is painted red, and the South pole might be painted blue.
- Most magnetic attraction occurs at the poles of the magnet.
- Even if you break a magnet, each piece will still have both a North and South pole.
- A magnet with only one pole doesn’t exist.
Finding Directions
Activity 4.3: Experimenting with a Magnet
- Objective: Understand how a magnet helps in finding directions.
- Steps:
- Suspend a bar magnet using a thread.
- Rotate the magnet and let it come to rest.
- Mark the positions of the ends on the ground and observe the direction.
- Results:
- The magnet aligns itself in the north-south direction.
- The end pointing north is the North pole, and the other is the South pole.
- This happens because Earth acts like a giant magnet.
Magnetic Compass:
- A device that uses a magnetized needle to find directions by always pointing to the North-South axis of the Earth.
How a Compass Works:
- When a bar magnet is suspended freely, it always aligns itself along the North-South direction.
- Sailors used this property to navigate before modern instruments were invented.
Building Your Own Compass (Activity 4.4):
- Materials: Cork, iron needle, magnet, bowl, water.
- Steps:
- Magnetize the needle by rubbing it with a magnet.
- Insert the needle into the cork and float it in water.
- Observe how the needle always points in the same direction.
- Magnetization: The process of making a material magnetic by rubbing it with a magnet.
- Fun Fact: Ancient Indians used a similar tool called matsya-yantra for navigation.
Attraction and Repulsion between Magnets
Activity 4.5: Testing Magnet Interaction
- Objective: Understand how magnets interact.
- Steps:
- Place a bar magnet on pencils.
- Bring another magnet close to it.
- Results:
- Unlike poles attract (North and South).
- Like poles repel (North-North or South-South).
Attraction and Repulsion:
- Like Poles Repel: North-North or South-South poles push away from each other.
- Unlike Poles Attract: North-South poles pull toward each other.
Identifying Magnets by Repulsion:
- Only magnets will repel each other; other metal objects won’t.
Activity 4.6: Magnetic Compass Interactions with a magnet
- Objective: Observe how a magnetic compass reacts to a nearby magnet.
- Steps:
- Place the compass and let it settle.
- Bring a bar magnet close and observe the needle.
- Results:
- The needle deflects away from the like pole (North-North).
- It moves closer to the opposite pole (North-South).
Activity 4.7: Investigating Magnetic Effects
- Objective: See if non-magnetic materials affect the magnetic field.
- Steps:
- Place materials like wood, cardboard, or plastic between a compass and a magnet.
- Results:
- The magnetic effect is not blocked by these materials.
- Magnetic fields can pass through non-magnetic materials.
Fun with Magnets
Reshma’s Magnet Activities:
- Reshma was excited to create fun magnet activities for her school fair. Here are some ideas:
- Magnetic Garland: Create a garland using magnets (Fig. 4.11). Use small magnets to create a chain or garland that sticks together.
- Steel Ball Maze: Move steel balls out of a maze by placing a magnet under a cardboard tray (Fig. 4.12).
- Magnet Fishing: Use a magnet to pick up a steel paper clip from water without getting wet (Fig. 4.13).
- Magnetic Cars: Test if two cars with magnets attached move toward each other or away when brought close (Fig. 4.14).
Care and Safety of Magnets
- How to Store Magnets:
- Keep bar magnets in pairs with opposite poles facing each other.
- Place wood or soft iron between them to protect their magnetic properties.
- Precautions:
- Magnets should not be heated, hammered, or dropped, as this can weaken their magnetic force.
- Keep magnets away from electronic devices like mobile phones, computers, and TVs, as they can interfere with the devices parts and can break down them.
- Have fun with magnets but handle them with care.
Chapter Summary:
- Magnet: A material that attracts certain metals like iron, nickel, and cobalt.
- Magnetic and Non-Magnetic Materials: Some materials are attracted to magnets, while others are not.
- Poles of a Magnet: A magnet has two poles—North and South—where its force is strongest.
- Magnetic Interactions: Like poles repel; unlike poles attract.
- Using a Compass: A compass helps find directions by aligning itself with Earth’s magnetic field.
- Fun Experiments: Create your own magnets or explore magnetic forces using everyday objects.
- Magnet Care: Proper storage and handling of magnets ensure they remain strong and effective.
