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.
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’.
,
Magnetic keepers are devices that are used to hold armatures in place in electric motors and generators. They are made of a ferromagnetic material, such as iron or steel, and are shaped so that they fit snugly around the armature. When the magnetic field is turned on, the keeper is attracted to the armature and holds it in place. This prevents the armature from moving and allows the motor or Generator to operate properly.
Magnetic keepers are also used in other applications, such as in switches and relays. They can be used to hold contacts in place or to prevent them from moving. Magnetic keepers are an important part of many electrical devices and systems.
Here are some of the subtopics of magnetic keepers:
Types of magnetic keepers
How magnetic keepers work
Applications of magnetic keepers
Advantages and disadvantages of magnetic keepers
Safety considerations when using magnetic keepers
How to choose the right magnetic keeper for your application
There are many different types of magnetic keepers, each with its own advantages and disadvantages. The most common type of magnetic keeper is the permanent magnet keeper. Permanent magnet keepers are made of a material that retains its magnetism even when the magnetic field is turned off. This makes them ideal for applications where the keeper needs to hold the armature in place even when the power is turned off.
Another type of magnetic keeper is the electromagnet keeper. Electromagnet keepers are made of a ferromagnetic material that is surrounded by a coil of wire. When current is passed through the coil, it creates a magnetic field that attracts the keeper to the armature. Electromagnet keepers are ideal for applications where the keeper needs to be turned on and off quickly.
How magnetic keepers work
Magnetic keepers work by using the principle of magnetism. When a magnetic field is applied to a ferromagnetic material, the material becomes magnetized. This means that the material will be attracted to other magnets. The strength of the attraction depends on the strength of the magnetic field and the type of ferromagnetic material.
In the case of a magnetic keeper, the magnetic field is created by the armature. When the armature is turned on, it creates a magnetic field that attracts the keeper. The keeper is then held in place by the magnetic field. When the armature is turned off, the magnetic field is removed and the keeper is released.
Applications of magnetic keepers
Magnetic keepers are used in a variety of applications, including:
Electric motors
Generators
Switches
Relays
Solenoids
Loudspeakers
Microphones
Hard drives
Compact discs
Advantages and disadvantages of magnetic keepers
Magnetic keepers have a number of advantages, including:
They are simple and inexpensive to manufacture.
They are reliable and durable.
They can be used in a variety of applications.
However, magnetic keepers also have some disadvantages, including:
They can be affected by external magnetic fields.
They can be damaged by high temperatures.
They can be corroded by moisture.
Safety considerations when using magnetic keepers
When using magnetic keepers, it is important to take the following safety precautions:
Keep magnetic keepers away from children and pets.
Do not use magnetic keepers near sensitive electronic equipment.
Do not use magnetic keepers in areas with high levels of electromagnetic radiation.
How to choose the right magnetic keeper for your application
When choosing a magnetic keeper for your application, it is important to consider the following factors:
The strength of the magnetic field required.
The type of ferromagnetic material to be used.
The size and shape of the keeper.
The cost of the keeper.
Where to buy magnetic keepers
Magnetic keepers can be purchased from a variety of sources, including:
Online retailers
Electrical supply stores
Hardware stores
Industrial supply stores
What is a magnetic keeper?
A magnetic keeper is a device that is used to hold a magnetic field in place. It is typically made of a ferromagnetic material, such as iron or nickel, and is shaped so that it can be placed around a magnet. When the keeper is placed around the magnet, it creates a magnetic field that is opposite to the field of the magnet. This causes the two fields to cancel each other out, and the magnet is held in place.
What are the different types of magnetic keepers?
There are two main types of magnetic keepers: permanent and temporary. Permanent magnetic keepers are made of materials that have a permanent magnetic field, such as iron or nickel. Temporary magnetic keepers are made of materials that have a temporary magnetic field, such as paper or plastic.
What are the benefits of using a magnetic keeper?
There are several benefits to using a magnetic keeper. First, it can help to keep a magnet in place. This can be useful for applications where the magnet needs to be held in a specific position, such as in a compass or a loudspeaker. Second, a magnetic keeper can help to protect a magnet from damage. This is because the keeper can absorb the shock of impact, which can prevent the magnet from being damaged. Third, a magnetic keeper can help to extend the life of a magnet. This is because the keeper can help to keep the magnet clean and free of dirt and debris, which can cause the magnet to lose its magnetism.
What are the drawbacks of using a magnetic keeper?
There are a few drawbacks to using a magnetic keeper. First, it can add weight to the magnet. This can be a problem for applications where weight is a concern, such as in a handheld device. Second, a magnetic keeper can add bulk to the magnet. This can be a problem for applications where space is limited, such as in a small electronic device. Third, a magnetic keeper can make the magnet more difficult to handle. This is because the keeper can make the magnet more slippery, which can make it difficult to grip.
How do I choose the right magnetic keeper?
When choosing a magnetic keeper, there are several factors to consider. The first factor is the type of magnet that you are using. If you are using a permanent magnet, you will need to choose a keeper that is made of a material that is compatible with the magnet. If you are using a temporary magnet, you can choose a keeper that is made of any material.
The second factor to consider is the size of the magnet. You will need to choose a keeper that is the same size or larger than the magnet. This will ensure that the keeper can properly hold the magnet in place.
The third factor to consider is the strength of the magnet. You will need to choose a keeper that is strong enough to hold the magnet in place. The strength of the keeper will depend on the strength of the magnet and the application.
The fourth factor to consider is the material of the keeper. You can choose a keeper that is made of a variety of materials, such as iron, nickel, or plastic. The material of the keeper will depend on the application and the Environment in which the magnet will be used.
The fifth factor to consider is the cost of the keeper. The cost of a keeper will vary depending on the type of material, the size, and the strength of the keeper.
Where can I buy a magnetic keeper?
Magnetic keepers are available from a variety of sources, including online retailers, hardware stores, and electronics stores.
Question 1
A permanent magnet is a magnet that does not require an external magnetic field to keep it magnetized. Which of the following is not a type of permanent magnet?
(A) Electromagnets are temporary magnets that are created by passing an electric current through a coil of wire. When the current is turned off, the electromagnet loses its magnetism.
Question 2
The strength of a permanent magnet is measured in units of gauss. Which of the following is the strongest type of permanent magnet?
(D) Neodymium magnets are the strongest type of permanent magnet. They are made from a combination of neodymium, iron, and boron.
Question 3
Permanent magnets are used in a variety of applications, including:
(A) Motors (B) Generators (C) Loudspeakers (D) All of the above
Answer
(D) Permanent magnets are used in a variety of applications, including motors, generators, loudspeakers, and many more.
Question 4
The magnetic field of a permanent magnet is strongest at the:
(A) North pole (B) South pole (C) Equator (D) None of the above
Answer
(A) The magnetic field of a permanent magnet is strongest at the north pole.
Question 5
The magnetic field of a permanent magnet can be used to attract or repel other magnets. Which of the following is true about the magnetic field of a permanent magnet?
(A) Like poles attract, unlike poles repel. (B) Like poles repel, unlike poles attract. (C) The magnetic field of a permanent magnet is always the same. (D) The magnetic field of a permanent magnet can be changed by applying an external magnetic field.
Answer
(A) Like poles attract, unlike poles repel. This is a fundamental law of magnetism.
Question 6
The magnetic field of a permanent magnet can be used to generate electricity. Which of the following is true about the magnetic field of a permanent magnet?
(A) The magnetic field of a permanent magnet can be used to generate electricity by moving it through a coil of wire. (B) The magnetic field of a permanent magnet can be used to generate electricity by applying an external magnetic field. (C) The magnetic field of a permanent magnet can be used to generate electricity by changing its shape. (D) All of the above
Answer
(D) The magnetic field of a permanent magnet can be used to generate electricity by moving it through a coil of wire, applying an external magnetic field, or changing its shape.
Question 7
The magnetic field of a permanent magnet can be used to create a force. Which of the following is true about the magnetic field of a permanent magnet?
(A) The magnetic field of a permanent magnet can be used to create a force by moving it through a coil of wire. (B) The magnetic field of a permanent magnet can be used to create a force by applying an external magnetic field. (C) The magnetic field of a permanent magnet can be used to create a force by changing its shape. (D) All of the above
Answer
(D) The magnetic field of a permanent magnet can be used to create a force by moving it through a coil of wire, applying an external magnetic field, or changing its shape.
Question 8
The magnetic field of a permanent magnet can be used to store information. Which of the following is true about the magnetic field of a permanent magnet?
(A) The magnetic field of a permanent magnet can be used to store information by changing its shape. (B) The magnetic field of a permanent magnet can be used to store information by applying an external magnetic field. (C) The magnetic field of a permanent magnet can be used to store information by moving it through a coil of wire. (D) All of the above
Answer
(A) The magnetic field of a permanent magnet can be used to store information by changing its shape. This is how hard drives work.
