Main topic information
Vocabulary/new concepts:
A magnet is a body that creates an invisible magnetic field around itself and exerts a magnetic force on other magnetised materials.
An electromagnet is a device that consists of a wire coil with an iron core and creates a magnetic field if an electric current is passed into its coil.
Magnetic induction lines are imaginary curves that help us imagine the strength and direction of a magnetic field in space.
The magnet in a compass is a thin arrow of magnetized iron or steel that rotates freely about a vertical axis on a sharp point. It is aligned along the lines of the force of the earth’s magnetic field. Through it, we can orient ourselves in space at any moment and determine directions – north, south, east, west.
A magnet is a body that creates an invisible magnetic field around itself and exerts a magnetic force on other magnetised materials. This field attracts or repels other magnetic materials that contain iron, nickel and cobalt. On bodies made of plastic, wood, paper, non-ferrous metals, etc. the magnet exerts no force.
According to their origin, magnets are divided into
- natural, created by nature – minerals that have magnetic properties, for example ,magnetite (black iron ore, used in ancient times for navigation), hematite, etc.;
- man-made – made of steel or special alloys.
Permanent magnets
Magnetic influence affects only bodies made of ferromagnetic substances (iron, cobalt, nickel). In addition to attracting objects containing iron, magnets interact with magnetic forces between themselves. Materials that create their magnetic field without an external source of energy and retain this property (their magnetizability) for a long time are called permanent magnets.
They are distinguished by the following characteristics:
- They are distinguished by permanent magnetic ability – this is their ability to retain their magnetic properties for a long time.
- They have two magnetic poles – north and south.
Source: https://depositphotos.com/vectors/science.html?qview=27298569
The ends of the bar magnet are called poles, and the space in the middle is called the neutral zone. Around the poles, the magnetic action is strongest, and around the neutral zone, it is weakest. The end of the magnet that points north is called the north magnetic pole, denoted by N (from the English word North). The other end, which points south, is called the south magnetic pole, denoted by S (from the English word South). They are most often depicted in red and blue and may be coloured differently in different sources.
Source: https://depositphotos.com/vectors/science.html?qview=665848976
- Opposite (differently named) magnetic poles attract, and identical (same-named) poles repel. The north pole of one magnet is attracted to the south pole of another magnet.
Source: https://www.yaclass.in/Exercise/PdfSolution?c=7e0bcd35-491b-4e7a-aaaa-cbcb25a17fd9&twId=20870&ts=1666693186&sg=un_7x0IkRARJQaQTRacDHCdYkgw1
- A magnetic field is created around them, which manifests itself by exerting a magnetic force on other magnetized bodies. The magnets need not be in immediate contact with each other to exert a force.
- Magnetic forces are invisible to the eye, act between magnetic materials and depend on the shape, size and distance between magnets. They increase when the distance between the poles decreases. As the distance from the source of the magnetic field increases, the effect of the magnetic force decreases until it disappears completely.
Electromagnets
An electromagnet is a device that consists of a wire coil with an iron core and creates a magnetic field if an electric current is passed into its coil.
Source: https://anzalweb.ir/wp-content/uploads/2018/02/FPO-electromagnet.jpg
Unlike permanent magnets, whose magnetization is constant, electromagnets can be switched on and off, as well as change the strength of their magnetic field. Depending on the needs, electromagnets can have different power ratings, have the flexibility and safety to be used in numerous devices and systems, and allow easy control over the strength and direction of their magnetic field.
That is why they are widely used in industry, in medicine, in transport, and in households.
Examples are electromagnetic cranes for lifting and moving heavy bulky objects in industry, separators, magnetic brakes, relays and electromagnetic valves in automation of various industries, hard disks and magnetic cards in electronics, electric motors in various vehicles, high-speed magnetic trains that run without contact with the rails, scanners and nuclear magnetic resonance in medicine, in scientific research (particle accelerators – cyclotrons) and many others.
High-speed train. Source: https://depositphotos.com/similar-images/244810236.html?qview=244238934
Earth’s magnetic field
Source: https://depositphotos.com/vectors/science.html?qview=308205136
The Earth’s magnetic field is a natural magnetic field that extends thousands of kilometres into space and surrounds our planet. Its shape is distorted by the solar wind (a stream of charged particles emitted from the Sun). The magnetic field is contracted on the side closer to the Sun, while it is elongated on the side further away. It protects the planet from the harmful radiation of solar particles.
The Earth’s magnetic field can be thought of as the field of a bar magnet passing through the centre of the planet. However, the magnetic and geographic poles of the Earth do not coincide. The magnetic poles are not fixed and move continuously. Their lines make an angle of about 120 to the Earth’s axis of rotation, but it is not fixed and can vary and have different values in different places.
See a short video simulation available at Earth’s Magnetic Lines – Science On a Sphere (noaa.gov)
The negative (south) pole of the magnet is located in the Arctic and is called the North Magnetic Pole, and its positive (north) pole is located in the Antarctic and is called the South Magnetic Pole. The field lines of the Earth’s magnetic field point from the north to the south pole of the magnet, i.e. from the Southern to the Northern Hemisphere.
It is important to note that the orientation of the Earth’s magnetic field has reversed more than once throughout the Earth’s geological history, with magnetic north becoming magnetic south and vice versa. This is called the inversion of the Earth’s magnetic field or geomagnetic inversion. However, this is a phenomenon that occurs once every few hundred years.
Interesting phenomena related to the interaction of charged particles from the solar wind with the Earth’s magnetic field are auroras.
Source: https://st5.depositphotos.com/19554348/65394/i/1600/depositphotos_653940658-stock-photo-northern-lights-starry-night-sky.jpg
Determination of directions, orientation
The Earth’s magnetic field is also used to determine the cardinal points of the world – north, south, east and west. The main tool for this is the magnetic compass. It consists of a thin pointer of magnetised iron or steel that rotates freely about a vertical axis on a sharp point. It is aligned along the field lines of the Earth’s magnetic field. The compass needle is always oriented along the line of the Earth’s magnetic field and points to magnetic north. It is housed in a case with a dial divided into degrees to read the direction in which the magnetic pointer points. In newer compasses, there are additional landmarks – measuring lines, a mirror, and a device for determining azimuth. Some factors, such as magnetic storms or anomalies, can affect the accuracy of the compass reading, but this does not make it a less reliable instrument for determining directions.
Source: https://st2.depositphotos.com/1005574/7343/v/600/depositphotos_73438351-stock-illustration-old-compass.jpg
Today, the exact location of the Earth’s surface is now determined using the GPS satellite system and modern smartphones.
