Magnets and Magnetic Field | Jamb(UTME)
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In this post, we have enumerated a good number of points from the topic Magnets and Magnetic Fields which was extracted
from the Jamb syllabus. I would advice you pay attention to each of the point knowing and understanding them by heart.
Happy learning
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The table of content below will guide you on the related topics pertaining to "Magnets and Magnetic Field" you can navigate to the one that captures your interest
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Table of Contents
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Jamb(utme) key points on natural and artificial magnets; magnetic properties of soft iron and steel; methods of making magnets and demagnetization
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Natural and Artificial Magnets
- Natural Magnets: Found in nature, like magnetite, which is a naturally occurring magnetic material.
- Artificial Magnets: Man-made magnets created by magnetizing materials like steel or alloys.
- Temporary Magnets: Artificial magnets that lose magnetism after some time, such as soft iron magnets.
- Permanent Magnets: Artificial magnets that retain their magnetism, made from materials like steel or alnico.
- Examples of Artificial Magnets: Bar magnets, horseshoe magnets, and electromagnets.
- Strength: Artificial magnets can be made stronger than natural magnets.
- Shape Variety: Artificial magnets can be shaped into specific forms to suit applications.
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Magnetic Properties of Soft Iron and Steel
- Soft Iron: Easy to magnetize and demagnetize.
- Steel: Harder to magnetize but retains magnetism for longer.
- Soft Iron Applications: Used in electromagnets and temporary magnetic cores.
- Steel Applications: Used to make permanent magnets.
- Retentivity: Steel has high retentivity, meaning it retains magnetism well.
- Coercivity: Soft iron has low coercivity, meaning it loses magnetism easily.
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Methods of Making Magnets
- Stroking Method: Rubbing a magnet over a material like steel in one direction.
- Electrical Method: Passing current through a coil wound around the material.
- Induction Method: Placing a material in a strong magnetic field.
- Heat and Magnetization: Heating a material and cooling it in a magnetic field to magnetize it.
- Direct Contact: Touching a magnetic material with a strong magnet to induce magnetism.
- Magnetizing with a Solenoid: Using a solenoid coil to create a magnetic field for magnetization.
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Demagnetization Methods
- Heating: Heating a magnet to its Curie point to lose magnetism.
- Hammering: Hitting a magnet repeatedly can disorganize its magnetic domains.
- AC Current: Passing alternating current through a coil wound around the magnet.
- Rough Handling: Dropping or mishandling a magnet can lead to loss of magnetism.
- External Magnetic Field: Exposing a magnet to a stronger opposing magnetic field.
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Concept of Magnetic Field
- Definition: The region around a magnet where its magnetic force is felt.
- Magnetic Lines of Force: Invisible lines that show the direction and strength of a magnetic field.
- Properties of Magnetic Lines: They never intersect, form closed loops, and are denser where the field is stronger.
- Direction: Magnetic field lines go from the north pole to the south pole outside the magnet.
- Visualization: Magnetic field lines can be observed using iron filings around a magnet.
- Magnetic Flux: A measure of the total magnetic field passing through an area.
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Magnetic Field of a Permanent Magnet
- Shape of Field: The magnetic field of a bar magnet is strongest at the poles.
- Uniformity: The field near the poles is stronger and more concentrated.
- Distance: The strength of the magnetic field decreases with distance from the magnet.
- Polarity: A magnet always has a north and a south pole.
- Dipole Nature: Permanent magnets are magnetic dipoles with opposing poles.
- Earth’s Magnetism: The Earth itself acts as a giant permanent magnet.
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Magnetic Field in Applications
- Compass: A compass needle aligns with the Earth’s magnetic field.
- Electric Motors: Magnets are crucial for converting electric energy to mechanical energy.
- Speakers: Use permanent magnets to produce sound through vibrations.
- Magnetic Storage: Used in hard drives and credit card strips.
- MRI Machines: Use strong magnetic fields for medical imaging.
- Transformers: Rely on soft iron cores to channel magnetic fields effectively.
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Magnetic Materials and Their Uses
- Ferromagnetic Materials: Strongly attracted to magnets, e.g., iron, nickel, cobalt.
- Paramagnetic Materials: Weakly attracted, e.g., aluminum.
- Diamagnetic Materials: Repelled by magnets, e.g., copper, bismuth.
- Magnetic Domains: Regions where magnetic moments are aligned in a material.
- Alignment: When magnetic domains align, the material becomes magnetized.
- Random Domains: In an unmagnetized material, magnetic domains are randomly oriented.
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Magnetic Fields in Conductors
- Current-Carrying Wire: Produces a circular magnetic field around it.
- Right-Hand Rule: Determines the direction of the magnetic field in conductors.
- Solenoid Field: A solenoid creates a uniform magnetic field inside it.
- Electromagnets: Temporary magnets created by passing current through a coil.
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Magnetic Poles
- Like Poles Repel: North repels north; south repels south.
- Unlike Poles Attract: North attracts south, and vice versa.
- Pole Strength: Concentrated at the ends of a magnet.
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Magnetic Field Interaction
- Superimposition: Multiple magnetic fields can combine to create a resultant field.
- Field Cancellation: Opposing fields can cancel each other out.
- Induced Magnetism: A magnetic field can temporarily magnetize nearby objects.
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Effects of Magnetic Fields
- Deflection of Moving Charges: Magnetic fields can influence moving charged particles.
- Field Variations: Field strength depends on distance and material properties.
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Jamb(utme) key points on magnetic field of a permanent magnet; magnetic field round a straight current carrying conductor, circular wire and solenoid
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Magnetic Field Around a Straight Current-Carrying Conductor, Circular Wire, and Solenoid
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Straight Current-Carrying Conductor
- The magnetic field around a straight conductor is circular in shape.
- The direction of the field is determined using the right-hand rule: curl your fingers around the conductor with the thumb pointing in the current's direction.
- The magnetic field strength decreases as the distance from the conductor increases.
- The field lines form concentric circles centered on the conductor.
- The magnetic field is stronger near the conductor.
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Circular Wire
- A current-carrying circular wire creates a magnetic field with lines forming loops.
- The magnetic field is strongest at the center of the loop.
- The field becomes weaker as you move away from the plane of the loop.
- The direction of the field inside the loop can be determined using the right-hand rule.
- Increasing the current in the wire strengthens the magnetic field.
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Solenoid
- A solenoid is a coil of wire that generates a magnetic field when current flows through it.
- Inside the solenoid, the field is nearly uniform and parallel to the solenoid's axis.
- The field outside the solenoid is weak and resembles that of a bar magnet.
- The magnetic field strength increases with more turns of the coil or higher current.
- The solenoid's poles can be determined using the right-hand rule.
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Properties of the Earth’s Magnetic Field
- The Earth acts as a giant magnet with its magnetic south pole near the geographic north pole.
- Magnetic field lines emerge near the south pole and re-enter near the north pole.
- The magnetic field strength is strongest near the poles and weakest at the equator.
- The Earth’s magnetic field protects the planet from charged particles in the solar wind.
- The field is dynamic and changes over time due to movements in the Earth's core.
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North and South Poles
- The magnetic north pole is the point where field lines point vertically downward.
- The magnetic south pole is the point where field lines point vertically upward.
- These poles are not fixed and slowly drift due to changes in the Earth’s magnetic field.
- The poles are used in navigation systems like compasses.
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Magnetic Meridian, Angle of Dip, and Declination
- The magnetic meridian is an imaginary vertical plane containing the Earth’s magnetic field lines.
- Angle of dip is the angle between the horizontal plane and the Earth’s magnetic field line at a given location.
- At the magnetic equator, the angle of dip is 0°.
- At the magnetic poles, the angle of dip is 90°.
- Magnetic declination is the angle between the geographic and magnetic meridians.
- Declination varies with location and changes over time.
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Magnetic Flux and Flux Density
- Magnetic flux is the total number of magnetic field lines passing through a surface.
- The unit of flux is the Weber (Wb).
- Flux density is the magnetic flux per unit area.
- The unit of flux density is Tesla (T).
- A stronger magnetic field has higher flux density.
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Variation of Magnetic Field Intensity Over the Earth’s Surface
- Magnetic field intensity varies depending on latitude.
- The intensity is stronger at the poles and weaker at the equator.
- The Earth’s field strength is affected by local geological formations.
- Temporary variations occur due to solar storms or magnetic field fluctuations.
- Long-term variations are caused by the movement of molten iron in the Earth’s outer core.
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Applications of Earth’s Magnetic Field
Navigation
- The Earth’s magnetic field enables the use of compasses for navigation.
- Compasses align with the magnetic field, pointing to the magnetic north pole.
- Modern navigation systems combine magnetic field data with GPS for accuracy.
- Sailors and pilots rely on the Earth’s magnetic field for directional guidance.
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Mineral Exploration
- Variations in the magnetic field are used to locate mineral deposits.
- Magnetic surveys help identify regions rich in iron ore and other magnetic materials.
- Geologists use instruments like magnetometers to map magnetic field variations.
- Magnetic anomalies indicate the presence of underground mineral resources.
- Exploration using magnetic data reduces the need for invasive methods.
- Magnetic mapping is essential for studying Earth's crust and tectonic activity.
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I recommend you check my article on the following:
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- Key Points and Summaries on 'Force on a Current-Carrying Conductor in a Magnetic Field' for Jamb(UTME Candidates)
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This is all we can take on "Jamb Physics Key Points and Summaries on Magnets and Magnetic Fields for UTME Candidates"
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