Magnets & Electromagnets - Class 6 Science Chapter 13
Magnets & Electromagnets – Class 6 Science Chapter 13
What is a magnet and What are magnetic poles?
A magnet is a piece of equipment that attracts specific materials like iron. I am sure you have seen bar magnets, such as the one illustrated in the figure below. This bar magnet, like other magnets, has two magnetic poles, i.e. north and south. The north pole is represented by the red end of the bar magnet, while the south is the blue end. These poles are the strongest points of a magnet. When magnets move, the poles always line up with the Earth’s north-south axis.
What is Magnetic Force and Magnetic Field?
Magnetic force is the force exerted by a magnet on certain materials, which also includes other magnets. The force is applied over a long distance and comprises both attractive and repulsive forces. Two magnets with opposite north and south poles attract each other, whereas two magnets with similar north and south poles repel each other. Magnetic fields enable magnets to exert force across a long distance.
Refer to the image below to see the magnetic field surrounding a bar magnet.
Iron filings, which are tiny particles of iron, were put under a sheet of glass. The magnet attracted the iron filings placed on the glass. The pattern of iron filings depicts the lines of force comprising the magnetic field. The concentration of iron filings at the poles suggests that these places are the most powerful. It is also possible to examine how the magnetic field affects the compasses positioned above the magnet.
Magnetic fields interact when two magnets come close. In the figure below, you can see how they interact. Lines of force from the north and south poles attract each other, but the lines of force from the two north poles repel each other.
Attraction and Repulsion
Magnets attract iron but may also repel other magnets.
When two magnets with similar or identical poles come close, they repel each other. For instance, the south pole of one magnet repels the south pole of another. In the same way, the north pole of one magnet repels the north pole of another.
When the opposite poles of two magnets come close, they attract one other. For instance, the south pole of one magnet attracts the north pole of another.
Precautions with Magnets
The following are some of the situations that might cause a magnet to be damaged –
Magnetism is lost when the magnet is heated, pounded, or dropped from a great height.
Magnets deteriorate without proper care.
The following tricks can preserve magnets –
Store them in pairs, with opposing poles on the same side.
Use a piece of wood to separate them.
Place two pieces of soft iron across their ends.
Place a piece of iron across the poles of a horseshoe magnet.
Magnets also have adverse effects on equipment. Keep magnets away from mobiles, TVs, music systems, CDs and the computer.
What is a magnetic force?
The magnetic force is the force exerted on an object due to its interactions with a magnetic field.
The newton (N) is the SI unit for magnetic force, while tesla (T) is the SI unit for the magnetic field.
Anyone who has handled two permanent magnets closes together has felt the existence of a magnetic force. When two south poles or north poles come close, the magnetic force is repellent, and the magnets push against each other in opposite directions. It is appealing to bring opposing poles to close together.
However, the moving charge is the underlying source of the magnetic field. At a microscopic level, the electrons in the atoms of magnetic materials move.
What is the equation of Magnetic Force?
The Lorentz force law describes the relationship between a magnetic field and the force felt by a moving charge or current. This law can be represented mathematically as a vector cross product:
For a charge (q) moving in magnetic field B with velocity v.
The magnitude of the result simplifies to
θ is the angle between v and B.
(So, the force is maximum when vand B are perpendiculars and 0 when both are parallel.)
Some important FAQs
How Do Magnets Work?
A moving electric charge creates a magnetic field. Magnets and magnetic fields are inextricably connected. Since electrons are particles with a negative charge, their motion around an atom’s nucleus generates a small magnetic field. However, there are many electrons in a material. The field generated by one electron gets cancelled out by another, resulting in no magnetism from the material.
However, certain materials behave differently. The magnetic field produced by one electron can influence the direction of the magnetic field produced by other electrons, causing them to align. It creates a magnetic “domain” within the material, in which all of the electrons have aligned magnetic fields. The materials that accomplish this are known as ferromagnetic at room temperatures. These materials help create permanent magnets.
A ferromagnetic material’s domains have random orientations. Even if nearby electrons align their fields together, other groups are likely to be aligned in a different direction. It results in no large-scale magnetism because distinct domains cancel each other out the same way that individual electrons do in other materials.
However, if an external magnetic field is applied to the material, for example, by bringing a bar magnet next to it – the domains begin to align. As all domains align, the entire material functionally becomes a single domain and produces two poles. These two poles become the north and south poles.
This alignment persists in the ferromagnetic materials even after the external field gets withdrawn. But in other materials (paramagnetic materials), the magnetic characteristics are lost when the external field gets removed.
What are the properties of a Magnet?
Magnets have the following properties –
Attracting magnetic materials;
Attracting the opposite poles of the other magnets;
Repelling similar poles of other magnets.
So, if you have two permanent bar magnets, bringing their north (or south) poles together generates a repulsive force that grows stronger as the two ends come close. When two opposed poles (north and south) come together, an attractive force exists between them. The closer they are, the greater this power becomes.
Ferromagnetic elements, such as iron, nickel, cobalt, or alloys containing them (such as steel), are attracted to permanent magnets even if they do not generate their magnetic field. They are attracted to magnets, and they do not repel till they start creating their magnetic field.
How does an electromagnet work?
A permanent magnet and electromagnet is not the same thing. Electromagnets, in a more visible form, employ electricity and are fundamentally created by the passage of electrons along a wire of electrical conductor. The passage of electrons along a wire, like the formation of magnetic domains, results in the formation of a magnetic field. The shape of the field is determined by the direction of the electrons – if you point your right hand’s thumb in the direction of the current, your finger curl in the direction of the field.
How to make an electromagnet?
Wound an electrical wire around a central core composed of iron. Pass current through the wire in circles around the central core to create a magnetic field along the coil’s centre axis.
If the electricity flow is interrupted, the charged electrons cease to move around the wire coil, and the magnetic field vanishes.
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