A magnet is any material that has the capability to attract iron and produce magnetic fields around itself. The oldest known descriptions of magnets and their characteristics are from Anatolia, China and India (2500 years ago). After the 12th century AD, magnetic compasses were widely used for navigation in Europe, China, the Arabian headland, etc. By the beginning of the 20th century, all the discovered elements and numerous compounds had been examined for magnetism. Most of the elements and compounds were found to possess some magnetic properties. Diamagnetism was the most common property among the materials. It is a fragile type of magnetism generated by a change in the electrons’ orbital motion due to an enforced magnetic field. When the source of the induced magnetic field is removed, the magnetisation of the given material will disappear.
A permanent magnet is a material made from a magnetised substance, and generates its own magnetic fields. A familiar example is a magnet used to stick notes on metal objects. Materials that are firmly attracted to magnets that also can be magnetised are known as ferromagnetic. Some common examples are nickel, cobalt and iron (including their alloys), a few alloys of rare-earth metals, and a few naturally existing minerals such as lodestone.
Temporary magnets consist of soft metals. These materials only show their magnetic properties when they are near an electric current or a permanent magnet field. They lose their magnetic properties gradually when they are withdrawn from the scope of the magnetic field. Soft iron and some iron alloys can be easily magnetised even in a weak magnetic field. However, they instantly lose their magnetism when the magnetic field is removed. These excellent temporary magnets are used in electrical devices like electric motors and telephones.
The video explains the concepts of magnets and magnetism.
An electromagnet is composed of a coil of wire that behaves like a magnet when an electrical current flows through it. The moment current flow stops, it will stop being a magnet. Usually, the coil is wrapped all over the core of a soft ferromagnetic compound such as mild steel. Such materials considerably enhance the magnetic field generated by the coil.
The symbol B stands for the value of magnetic flux density within a magnetised object. The symbol H stands for the value of a magnetic field or magnetising force generating it. The two quantities can be denoted by the equation B= μH, where μ stands for the material’s permeability. It is a measure of the magnetisation’s intensity that can be generated by a specified magnetic field.
Important Magnet Question with Answers
1) What is a magnet?
A magnet is any material that has the capability to attract iron and produce magnetic fields around itself. Most of the elements and compounds were found to possess some magnetic properties.
2) Where do the oldest known descriptions of magnets come from?
The oldest known descriptions of magnets and their characteristics are from Anatolia, China and India (2500 years ago). After the 12th century AD, magnetic compasses were widely used for navigation in Europe, China, the Arabian headland, etc. By the beginning of the 20th century, all the discovered elements and numerous compounds had been examined for magnetism.
3) What are the two poles of a magnet?
The north pole and south pole are the two poles of a magnet. The end that aligns with the north is considered the north pole. The other end is considered the south pole.
4) What is meant by diamagnetism?
Diamagnetism is a fragile type of magnetism generated by a change in the electrons’ orbital motion due to an enforced magnetic field. When the source of the induced magnetic field is removed, the magnetisation of the given material will disappear.
5) What is a permanent magnet?
A permanent magnet is a material made from a magnetised substance, and generates its own magnetic fields. A familiar example is a magnet used to stick notes on metal objects.
6) What are ferromagnetic materials?
Materials that are firmly attracted to magnets that also can be magnetised are known as ferromagnetic. Some common examples are nickel, cobalt and iron (including their alloys), a few alloys of rare-earth metals, and a few naturally existing minerals such as lodestone.
6) What are temporary magnets?
Temporary magnets consist of soft metals. These materials only show their magnetic properties when they are near an electric current or a permanent magnet field. They lose their magnetic properties gradually when they are withdrawn from the scope of the magnetic field. Soft iron and some iron alloys can be easily magnetised even in a weak magnetic field. However, they instantly lose their magnetism when the magnetic field is removed. These excellent temporary magnets are used in electrical devices like electric motors and telephones.
7) What is an electromagnet?
An electromagnet is composed of a coil of wire that behaves like a magnet when an electrical current flows through it. The moment current flow stops, it will stop being a magnet. Usually, the coil is wrapped all over the core of a soft ferromagnetic compound such as mild steel. Such materials considerably enhance the magnetic field generated by the coil.
8) Magnetism is caused by the _____ of electric charges.
Answer: Motion
Explanation: Magnetism is caused by the motion of electric charges.
9) What does the symbol B and H represent in magnetism?
The symbol B stands for the value of magnetic flux density within a magnetised object. The symbol H stands for the value of a magnetic field or magnetising force generating it. The two quantities can be denoted by the equation B= μH, where μ stands for the material’s permeability. It is a measure of the magnetisation’s intensity that can be generated by a specified magnetic field.
10) Write an essay on the daily life uses of magnets.
Debit, credit and ATM cards have a magnetic strip on one of their sides. This strip encrypts the information of the user’s financial institution and links it with their account.
Old televisions (CRT model)) and old large computer monitors contain a cathode ray tube that works on an electromagnet to direct electrons to the screen.
VHS tapes consist of a roll of magnetic tape. The data that forms the sound and video is embedded in the magnetic overlay on the tape.
Most of the microphones and speakers use a current-carrying coil and a permanent magnet to transform the signal or electric energy into mechanical energy (motion that generates the sound). The coil is enveloped around a reel connected to the speaker cone, and bears the signal as a varying current that interacts with the permanent magnet’s field.
Several types of electric motors depend upon a combination of a permanent magnet and an electromagnet. Just like loudspeakers, they transform electric energy into mechanical energy. A generator uses the reverse principle: it transforms mechanical energy into electric energy by displacing a conductor along a magnetic field.
Electric guitars employ magnetic pickups to convert the vibration of guitar strings into electric currents for amplification. This is in contrast to the concept behind the dynamic microphones and speakers because the vibrations are recognised straight by the magnet (no diaphragm is used).
Chemists employ nuclear magnetic resonance to identify manufactured compounds. Hospitals employ magnetic resonance imaging equipment to detect issues in a patient’s organs without surgery.
A compass has a magnetic pointer suspended to orient itself with a magnetic field. It will deflect according to the direction in which it is placed, relative to the Earth’s magnetic field.
Due to the magnets’ ability to counter the gravitational force at close range, magnets are often used in children’s toys.
Magnets can be used to pick up magnetic objects that are too small or out of reach. Several types of screwdrivers are magnetised for this use. Magnets are used in salvage and scrap operations to segregate magnetic metals from non-magnetic metals.
Magnets can also be used in fail-safe devices for some cable connections. The power cords of some electronic devices are magnetic to avoid accidental impairment to the port when tripped over. The power connection that uses Magsafe in the Apple MacBook is an example of it.
Magnetic levitation transport (maglev) is a type of transportation system that suspends, propels and guides vehicles through electromagnetic force. It efficiently reduces rolling resistance, enabling vehicles to move with tremendous speed (compared to conventional vehicles).
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Practice Questions
1) What is a magnetic field?
2) What is meant by magnetic flux density?
3) What is a magnetic monopole?
4) Explain the origin of the Earth’s magnetic field.
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