![]() However as discussed before, it can also be used to magnetize a material if positioned correctly and hammered within a set external magnetic field since the domains will reposition itself accordingly. Physical impact on a ferromagnetic material will randomize the orientation of the domains and therefore demagnetize it. Since the direction of current determines the polarity of the magnet, it is important to understand that the current must flow in a single direction (direct current) in order to magnetize the metal. You can actually deduce the polarity of the electromagnet by looking at the direction of the current at the ends of the solenoid. The magnetism can be strengthened and weakened by adjusting the voltage of the electricity. Once the electricity is turned off, the magnetism will also switched off along with it. The metal inside the coil is called a solenoid. This whole set up is called an electromagnet. Therefore if you look at the diagram above, current will actually be flowing in the opposite direction of the arrows. This means that current is always going in the direction opposite to electron flow. VERY IMPORTANT NOTE: Conventional current is the flow of positive charge. Ferromagnetic materials can be magnetized by placing them inside the coil like so: The pattern of field lines outside the coil is identical to a bar magnet. When a direct (unidirectional) current flows through a coil of wire, a magnetic field is created around and inside the coil. ![]() The right hand grip rule can be very handy here (no pun intended): The direction of the magnetic field depends on the direction of the current (from + to – around the circuit). When a direct (unidirectional) current flows through a wire, a magnetic field is produced around the wire. Magnetization via electricity (direct current) Stroking will align the domains in the ferromagnetic material and magnetize it. The Earth’s magnetic field will then reposition the domains into a new orientation parallel with the Earth’s magnetic field. The impact of the hammer with the iron nail causes the magnetic domains within the nail to break loose from their current orientation. Strike an iron nail squarely and sharply several times with a hammer while keeping the nail positioned in a north-south orientation. Here we will go through certain techniques that are known to work well in doing this. Recall above that magnetism can be induced in ferromagnetic materials. Otherwise small iron fillings can be sprinkled around the magnet and they too will line up with the magnetic field and show the field lines. If small plotting compasses are placed around a bar magnet, the compasses show the direction of the magnetic field. It will remain magnetised until it is banged on the table or dropped (causing the domains to randomize). Compared to iron, steel is less strongly magnetized by permanent magnets but it will retain some if its induced magnetism and become a permanent magnet. Steel is made of iron and carbon, so it is also ferromagnetic. ![]() However as soon as you remove the magnet, the iron domains will immediately randomize again and thus it loses its temporary magnetism. The iron domains (which also have a north and south pole) will orientate themselves accordingly.Įssentially once the domains line up like this, the iron has now become a magnet itself i.e. However, when the iron is placed near a permanent magnet, the domains line up because they are attracted by the magnet. In an unmagnetized piece of iron the domains are arranged randomly. These materials are called ferromagnetic materials and they have the ability to become magnetized.įerromagnetic materials contain what we can think of as tiny magnets called domains. There are certain materials (such as iron) that are always attracted to magnetic poles (north & south). We will look at this in more detail down below.įor now here are some basic rules of magnetic interaction: However they can become magnetized and become magnets if their domains become aligned. Magnetic materials such as iron aren’t exactly magnets (yet) because the domains have a random orientation. In a permanent magnet, these domains are well aligned in a certain direction which give the magnet its north and south pole. If it is free to rotate it will point towards the Earth’s north pole.Īll permanent magnets are made of smaller magnets that we call domains. A north magnetic pole is actually a north seeking pole, i.e. ![]() Magnetic forces are due to the interactions between magnetic fields.Īll magnets have a north and south pole. ![]()
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