A magnet keeper, also known historically as an armature, is a ferromagnetic bar made from soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have a low magnetic coercivity, such as Alnico magnets.
Keepers also have a useful safety function, as they stop external Metal being attracted to the magnet. Most magnets do not need a keeper, only those with low coercivity, meaning that they are easily susceptible to stray fields. Magnet can be considered as the sum of many little magnetic domains, which may only be a few micrometers or smaller in size. Each domain carries its own small Magnetic Field, which can point in any direction. When all of domain are pointing in the same direction, the fields add, yielding a strong magnet. When these all point in random directions, they cancel each other, and the net magnetic field is zero.
In magnets with low coercivity, the direction in which the magnetic domains are pointing is easily swayed by external fields, such as the Earth’s magnetic field or perhaps by the stray fields caused by flowing currents in a nearby electrical circuit. Given enough time, such magnets may find their domains randomly oriented, and hence their net magnetization greatly weakened. A keeper for low-coercivity magnets is just a strong permanent magnet that keeps all the domains pointing the same way and realigns those that may have gone astray.
Magnetic lines of force and their properties
To describe the phenomena related to magnets, lines are used to depict the force existing in the area surrounding the magnet. These lines are called the magnetic lines of force. These lines do not exist actually, but are imaginary lines that are used to illustrate and describe the pattern of the magnetic field. As shown in the figure below, the magnetic lines of force are assumed to originate from the north pole of a magnet, then pass through the surrounding space and then arrive at the South Pole. Then these lines travel inside the magnet from the South Pole to the North Pole and hence complete the loop.
Lines of force are the lines in any such field the tangent of which at any point gives the field direction at that point and its density gives the magnitude of the field. Hence, magnetic lines of force are basically the lines of force which represent the direction of the magnetic field. The imaginary path traced by an isolated (imaginary) unit north pole may also be defined as a line of force. Magnetic lines of force are closed curves. Outside the magnet their direction is from north pole to south pole and inside the magnet these are from south to north pole.
They don’t have any origin or end and do not interact because if they do so then it would mean two value of magnetic field at a single point, which is not possible. At the poles of the magnet the magnetic field is stronger because the lines of force there are crowded together and away from the poles the magnetic field is week. i.e. magnetic field intensity depends on the number of lines of force. The number of magnetic lines of force passing through unit normal area is defined as magnetic induction whereas the number of lines of force passing through any area is known as magnetic flux. The lines of force can emerge out of the north pole of magnet at any angle and these can merge into the South Pole at any angle.
The direction of magnetic line of force is the direction of force on a North Pole, so the magnetic lines of force always begin on the North Pole of a magnet and end on the South Pole of the magnet. When a small magnetic compass is placed along a lie of force, it sets itself along the line tangential to it. Hence, the line drawn from the South Pole of the compass to its North pole shows the direction of the magnetic field.
Plotting the lines of force Terrestriel Magnetism
The space around a magnet, where magnetic force can be felt by a magnetic body is called the magnetic field of that magnet. The field can be represented by lines, called magnetic lines of force. A magnetic line of force is a line, straight or curved, the tangent to which at any point gives the direction of the magnetic field at that point.
When two magnetic field i.e. magnetic field of earth’s magnet and bar magnet acts in the same place, the resultant field has a special character. When we placed the magnetic needle at any particular point, then the needle does not show any direction at that point as there is no net magnetic field at that point. This point is known as a null point or neutral point.
The given figure A and B show the neutral point. Here, in figure A, when north pole of the magnet points south and magnet in the magnetic meridian, the horizontal component of the earth’s magnetic field and bar magnet becomes equal and opposite in point X, which is the neutral point. In figure B, when the north pole of the magnet points geographic north, the neutral point lie towards the lateral side at point X.
A neutral point in a magnetic field is a point at which the horizontal component of earth’s magnetic field and the magnetic field due to the magnet are exactly equal and opposite. At the neutral point, the lines of force will not pass and compass needle will not point in any fixed direction. In other words, ‘A neutral point in a magnetic field is a point at which the horizontal component of earth’s magnetic field and the magnetic field due to the magnet are exactly equal and opposite. At the neutral point, the lines of force will not pass and compass needle will not point in any fixed direction’.
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Magnetic Keepers
Magnetic keepers are devices that are used to retain the magnetism of a magnet. They are typically made of a soft ferromagnetic material, such as iron or nickel. When a magnet is placed near a magnetic keeper, the keeper will attract the magnet and cause it to become more strongly magnetized.
Magnetic keepers work by providing a path for the magnetic field lines to flow through. The magnetic field lines will always try to take the shortest path from the north pole of a magnet to the south pole. When a magnetic keeper is placed near a magnet, the magnetic field lines will flow through the keeper and cause the magnet to become more strongly magnetized.
Magnetic keepers are used in a variety of applications, including:
- Restoring the magnetism of a magnet that has lost its magnetism
- Preventing a magnet from demagnetizing
- Holding a magnet in place
Magnetic keepers are an important part of many magnetic devices. They help to ensure that magnets are always working properly and that they do not lose their magnetism.
Magnetic Lines of Force and Their Properties
Magnetic lines of force are invisible lines that represent the direction of the magnetic field around a magnet. The lines of force always start at the north pole of a magnet and end at the south pole. The closer the lines of force are together, the stronger the magnetic field is.
The properties of magnetic lines of force include:
- They are always perpendicular to the surface of a magnet.
- They are always in a closed loop.
- The closer the lines of force are together, the stronger the magnetic field is.
Magnetic lines of force can be used to visualize the magnetic field around a magnet. To do this, you can use a compass or a bar magnet. Place the compass or bar magnet near the magnet you want to visualize the magnetic field for. The direction of the magnetic field will be indicated by the needle of the compass or the north pole of the bar magnet. Draw a line in the direction of the magnetic field. Repeat this process for several points around the magnet. The lines of force will be the lines that connect all of the points you have drawn.
Plotting the Lines of Force
Plotting the lines of force is a way of visualizing the magnetic field around a magnet. To plot the lines of force, you can use a compass or a bar magnet. Place the compass or bar magnet near the magnet you want to plot the lines of force for. The direction of the magnetic field will be indicated by the needle of the compass or the north pole of the bar magnet. Draw a line in the direction of the magnetic field. Repeat this process for several points around the magnet. The lines of force will be the lines that connect all of the points you have drawn.
The lines of force will be strongest near the poles of the magnet and will become weaker as you move away from the poles. The lines of force will also be closer together near the poles and will become further apart as you move away from the poles.
Terrestrial Magnetism
Terrestrial magnetism is the study of the Earth’s magnetic field. The Earth’s magnetic field is generated by the movement of molten iron in the Earth’s core. The magnetic field protects the Earth from harmful radiation from the sun and other sources. It also helps to guide birds and other animals during Migration.
The Earth’s magnetic field is not uniform. It has two main components: the dipole field and the non-dipole field. The dipole field is the strongest component of the Earth’s magnetic field. It is generated by the movement of molten iron in the Earth’s core. The non-dipole field is weaker than the dipole field. It is generated by other factors, such as the Earth’s rotation and the Earth’s Atmosphere.
The Earth’s magnetic field is constantly changing. The dipole field is slowly decaying. The non-dipole field is also changing, but it is more variable than the dipole field. The changes in the Earth’s magnetic field are caused by the movement of molten iron in the Earth’s core.
The Earth’s magnetic field is important for life on Earth. It protects us from harmful radiation from the sun and other sources. It also helps to guide birds and other animals during migration.
Magnetic Keepers
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What is a magnetic keeper?
A magnetic keeper is a device that is used to keep a magnet from losing its magnetism. It is typically made of a ferromagnetic material, such as iron or steel, and is placed near the poles of the magnet. The magnetic field of the keeper interacts with the magnetic field of the magnet, and this interaction helps to keep the magnet in its polarized state. -
How do magnetic keepers work?
Magnetic keepers work by creating a magnetic field that opposes the natural tendency of a magnet to demagnetize. When a magnet is placed near a magnetic keeper, the magnetic field of the keeper interacts with the magnetic field of the magnet. This interaction creates a force that opposes the demagnetizing force, and this helps to keep the magnet in its polarized state. -
What are the different types of magnetic keepers?
There are two main types of magnetic keepers: permanent magnetic keepers and temporary magnetic keepers. Permanent magnetic keepers are made of materials that retain their magnetism even when they are not in the presence of a magnetic field. Temporary magnetic keepers are made of materials that lose their magnetism when they are not in the presence of a magnetic field. -
What are the advantages and disadvantages of using magnetic keepers?
The main advantage of using magnetic keepers is that they can help to keep a magnet from losing its magnetism. This can be useful in applications where it is important to maintain the magnetic properties of a magnet, such as in motors and generators. The main disadvantage of using magnetic keepers is that they can add weight and bulk to a device.
Magnetic lines of force and their properties
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What are magnetic lines of force?
Magnetic lines of force are imaginary lines that represent the direction of the magnetic field around a magnet. The magnetic field is strongest at the poles of the magnet and weakest in the middle. -
What are the properties of magnetic lines of force?
Magnetic lines of force are always continuous. They never cross each other. They emerge from the north pole of a magnet and enter the south pole. -
How can you plot the lines of force around a magnet?
You can plot the lines of force around a magnet by sprinkling iron filings around the magnet. The iron filings will align themselves with the magnetic field and will form a pattern that represents the lines of force.
Terrestriel magnetism
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What is terrestriel magnetism?
Terrestriel magnetism is the magnetic field of the Earth. The Earth’s magnetic field is generated by the movement of molten iron in the Earth’s core. The magnetic field protects the Earth from harmful radiation from the sun and other sources. -
What are the properties of the Earth’s magnetic field?
The Earth’s magnetic field is a dipole field, which means that it has two poles, a north pole and a south pole. The north pole of the Earth’s magnetic field is located near the geographic south pole, and the south pole of the Earth’s magnetic field is located near the geographic north pole. The Earth’s magnetic field is not perfectly aligned with the Earth’s axis of rotation. The magnetic field is tilted at an angle of about 11 degrees to the Earth’s axis of rotation. The Earth’s magnetic field is also not constant. It changes over time, and the strength of the magnetic field varies from place to place. -
What are the effects of the Earth’s magnetic field?
The Earth’s magnetic field protects the Earth from harmful radiation from the sun and other sources. The magnetic field also affects the Earth’s atmosphere and Climate. The magnetic field is used by navigation systems, such as compasses.
- A magnetic keeper is a device used to keep a permanent magnet from losing its magnetism. True or False?
- Magnetic lines of force are imaginary lines that represent the direction of the magnetic field. True or False?
- The properties of magnetic lines of force include:
(a) They are always perpendicular to the surface of a magnet.
(b) They are always directed from the north pole of a magnet to the south pole of a magnet.
(c) They are always crowded together near the poles of a magnet and spread out further away from the poles.
(d) All of the above. - To plot the lines of force of a magnet, you can use a compass. True or False?
- Terrestriel magnetism is the study of the Earth’s magnetic field. True or False?
Answers:
1. True
2. True
3. (d)
4. True
5. True
Here are some additional details about each topic:
- A magnetic keeper is a device used to keep a permanent magnet from losing its magnetism. It does this by providing a path for the magnetic field lines to flow through, which prevents them from escaping from the magnet.
- Magnetic lines of force are imaginary lines that represent the direction of the magnetic field. They are always perpendicular to the surface of a magnet and are always directed from the north pole of a magnet to the south pole of a magnet. They are also always crowded together near the poles of a magnet and spread out further away from the poles.
- The properties of magnetic lines of force can be summarized as follows:
- They are always perpendicular to the surface of a magnet.
- They are always directed from the north pole of a magnet to the south pole of a magnet.
- They are always crowded together near the poles of a magnet and spread out further away from the poles.
- To plot the lines of force of a magnet, you can use a compass. To do this, place the compass near the magnet and observe the direction in which the needle points. The lines of force will be perpendicular to the needle. Repeat this process at several points around the magnet to create a map of the lines of force.
- Terrestriel magnetism is the study of the Earth’s magnetic field. The Earth’s magnetic field is generated by the movement of molten iron in the Earth’s core. The field is strongest at the poles and weakest at the equator. The Earth’s magnetic field protects us from harmful radiation from the sun.