Magnetism: Bar Magnet and Modern Applications

Magnetism, a natural phenomenon that has intrigued mankind since ancient times, is a vital element in many modern technologies and applications. This chapter delves deep into the mysterious world of magnets, their discovery, and their varied uses. From the basic principles of magnetic effects on electric current to their application in medicine and everyday life, the nuances of magnetism are meticulously dissected to provide a comprehensive understanding.

Fun with Magnets: Bar Magnet Wonders in Everyday Delights

• Many everyday items, like stickers on refrigerators or pin holders, use magnets.  These items often conceal their magnets, making them appear “magical” in their ability to stick or attract metal.

Discovery of Magnets: Mythical Discoveries to Modern Creations

• Legend suggests that magnets were discovered by a shepherd named Magnes in ancient Greece. 
• His stick, with an iron tip, got attracted to a rock, which turned out to be a natural magnet called magnetite.  
• The name might have originated either from the shepherd or a place called Magnesia.
• Such rocks, which attracted iron, were later termed magnets. 
• Over time, humans realized they could create their own magnets, leading to the development of artificial magnets.
• Today, artificial magnets come in various shapes like bar magnets, horseshoe magnets, and cylindrical magnets. 

Magnetic Experiment: Invisible Forces in Simple Experiments

• An experiment can demonstrate the invisible force of magnets. 
• By placing a magnet inside a cup and hanging an iron clip on a short thread near the cup, the magnet, unseen inside the cup, can attract the clip, making it seem like the clip hovers in the air by some unseen force.

Magnetic and Non-Magnetic Materials: Materials and Soil Secrets

• By retracing the steps of Magnes, one can explore the magnetic nature of objects around them. 
  • A simple way to do this is by attaching a magnet to a stick, termed as the “Magnes stick”,.
  • And using it to determine which objects it attracts in various environments like a school playground or a classroom.
• Objects attracted by the magnet are made of magnetic materials like iron, nickel, or cobalt. 
  • On the other hand, materials that aren’t attracted by the magnet are termed non-magnetic. 
  • One can use the observations from the table to identify which materials are non-magnetic.
• An interesting experiment involves rubbing a magnet in sand or soil. 
  • Upon extraction, one might notice particles sticking to the magnet. 
  • While many of these particles can be shaken off, some stubborn ones remain. 
  • These particles are typically iron filings present in the soil. 
  • This activity helps deduce the presence of iron in different soil or sand samples.
• By documenting the amount of iron filings found in various soil samples, one can compare the iron content from different regions. 
  • Sharing this information can provide insights into the varying magnetic properties of soils from different parts of the country.

Poles of a Magnet: Patterns and Shapes

• When a magnet is rubbed in soil, it attracts iron filings, if present.
• Interestingly, these filings don’t stick uniformly all over the magnet. 
  • An activity using a sheet of paper and some iron filings demonstrates this behavior. 
  • Placing a bar magnet on the paper reveals that certain areas of the magnet attract more iron filings than others. 
  • Repetition of this activity confirms a consistent pattern in the distribution of the iron filings. 

• This distinct attraction is more pronounced near the two ends of the bar magnet. 
  • These specific regions are termed as the “poles” of the magnet. 
  • Magnets of different shapes also have poles, which can be identified using the same method with iron filings. 
  • By observing and experimenting with various magnets, one can deduce and mark the location of poles for different magnet shapes.

Finding Directions with Magnets

• From ancient times, the unique properties of magnets have been harnessed to find directions. 
  • A famous anecdote revolves around Emperor Hoang Ti of China, who used a rotating statue on his chariot that always pointed south, helping him navigate unfamiliar territories. 
• You can replicate this directional attribute of magnets by suspending a bar magnet, allowing it to rotate freely. 
  • When left undisturbed, the magnet consistently aligns itself in the North-South direction. 
  • When you push the magnet in different directions and let it settle, it will invariably return to this North-South orientation. 

• Using the rising sun as a general indicator of the east direction, you can determine the North. 
  • With this method, the magnet’s end pointing North is termed the North pole or North seeking end, while the other end pointing South is termed the South pole or South seeking end. 
  • This inherent quality of magnets has been invaluable for travelers over centuries.

• This magnetic property eventually led to the invention of the compass.
  •  A compass consists of a magnetized needle that can pivot freely inside a marked dial. 
  • When settled, the needle indicates the North-South direction. 
  • The needle’s north pole is typically differentiated by a distinct color. 
  • By using a compass, navigators and explorers have been finding their way for ages, proving the indispensable nature of this magnetic tool.

Creating Your Own Magnet and Compass: Bar Magnet Secrets and Ancient Wisdom

• You can easily transform a regular iron piece into a magnet. 
  • To do this, take an iron bar and stroke it with a bar magnet from one end to the other, ensuring you use the same pole and move in the same direction consistently. 

• After about 30-40 strokes, the iron bar will become magnetized, which can be tested by bringing it close to a pin or iron filings.
• Once you’ve made a magnet, you can create a simple compass. 
• Magnetize an iron needle with your new magnet. 
  • Then, insert this needle through a small piece of cork or foam, ensuring it doesn’t touch the base. 
  • Place this setup on water in a bowl, allowing the cork to float freely.  

• The magnetized needle will align itself with the Earth’s magnetic field, pointing towards the North-South direction. 
  • No matter how you rotate the floating cork, once it stabilizes, the needle will consistently point in the same direction, giving you a rudimentary compass.

Attraction and Repulsion between Magnets: Bar Magnet Interactions and Precautions

• When experimenting with magnets placed on toy cars, we observe some intriguing behaviors. 
  • If a car with the south pole of a magnet facing forward (Car A) is placed near another car with its north pole facing forward (Car B), the two cars attract each other.
  •  If the opposite poles of the magnets face each other, they attract. 

• However, when similar poles face each other, they repel. 
• This property can also be observed by suspending a magnet and bringing the poles of another magnet near it. 
  • Like poles repel, and unlike poles attract each other.

• It’s important to handle magnets with care. 
• Their magnetic properties can diminish if subjected to heat, impact, or if they’re mishandled. 
  • For storage, bar magnets should be paired with unlike poles together, separated by wood, and capped with soft iron pieces at their ends. 

• Horse-shoe magnets should have an iron piece across their poles. 
• Also, magnets should be kept away from electronic devices like televisions, mobile phones, cassettes, CDs, and computers to prevent potential damage.

DOWNLOAD PDF