TJC 2023 IP4 Magnetism Notes.pdf

TJC IP4 PHYSICS IP4 Physics Topic 15 – Magnetism Page 1 of 10 Student’s Copy Topic 15: Magnetism Content • Laws of magnetism • Magnetic properties of matter • Magnetic field Learning Outcomes Candidates should be able to: (a) state the properties of magnets (b) describe induced magnetism (c) describe electrical methods of magnetisation and demagnetisation (d) draw the magnetic field pattern around a bar magnet and between the poles of two bar magnets (e) describe the plotting of magnetic field lines with a compass (f) distinguish between the properties and uses of temporary magnets (e.g. iron) and permanent magnets (e.g. steel)

TJC IP4 PHYSICS IP4 Physics Topic 15 – Magnetism Page 2 of 10 Student’s Copy 1 Introduction We can observe that the magnets interact even when they are they are not in direct contact. In electrostatics, we used the idea of an electric field to account for the interaction between charges that were separated from one another. In the same way, we can use the idea of magnetic field to account for the magnetic interaction. Every magnet has two poles. This is where most of its magnetic strength is most powerful. These poles are called north and south poles. The poles are called this as when a magnet is hung or suspended the magnet lines up in a north - south direction. Like poles repel each other while unlike poles attract. The attraction or repelling of two magnets depend on how close they are to each other and how strong the magnetic field of each magnet is. 1.1 Properties of Magnets LO (a) All magnets have the following properties: • Magnetic poles: Sprinkle iron filings onto a bar magnet and most of them attracted to the two ends of the bar magnet. These two ends are known as poles of the magnet. They are the locations where the magnetic effects are the strongest. • North and South poles: When a bar magnet is suspended freely, it will come to rest in the North-South direction. The end of the bar magnet that points to the northern end of the Earth is called the north-seeking pole, North pole or N pole. The other end is known as the south-seeking pole, South pole or S pole. • Law of magnetism: Like poles repel, unlike poles attract. [parallel to what has been taught in Static Electricity: Law of electrostatics] • Attracts magnetic materials : Cobalt,Iron, Nickel & Steel (Mnemonic: CoINS) 1.2 The Earth’s Magnetic Field Because of Earth's magnetic field, a compass placed anywhere on Earth turns so that the "north pole" of the magnet inside the compass points roughly north, toward Earth's north magnetic pole in northern Canada. This is the traditional definition of the "north pole" of a magnet, although other equivalent definitions are also possible. One confusion that arises from this definition is that if Earth itself is considered as a magnet, the south pole of that magnet would be the one nearer the north magnetic pole, and vice-versa. (Opposite poles attract and the north pole of the compass magnet