## 05 Electricity and Magnetism

Electricity & Magnetism. In this section, learners explore the diversity of phenomena related to the fundamental physical property of (electric) charge, which experiences forces when interacting with electric and magnetic fields. There is a close analogy between mass in a gravitational fields and charge in an electric field. Electromagnetic forces can cause the kinds of motion studied in the earlier mechanics topics, and the microscopic behaviour of individual charges is connected to macroscopic property of current in circuit systems. The principle of conservation of energy guides the analysis of circuits containing resistors and e.m.f. sources. In H2 Physics, the consideration of charge storage in capacitors deepens learners’ appreciation of applications in electronics. The mathematics of oscillations and waves prove useful here for describing alternating currents in the electrical grid. In H3 Physics, the laws of electromagnetism are recast in integral form, which emphasises their geometrical nature, and allows characterisation of more complex field patterns. Learners explore the rotational motion of electric and magnetic dipoles, as well as the modification of electromagnetic fields in dielectric and ferromagnetic media, which is crucial for technological applications. In electrical circuits, the analogy with mechanical oscillations is established when inductive components are added to resistive and capacitive components.

Big ideas1. Electrical charge is a property of matter. Electrons can be transferred from one place to another, but cannot be created or destroyed. 2. Electricity is one of the most common means by which we transfer energy; the electrical current (moving charges) brings us energy from power plants when there is a complete (closed) circuit from the power plants to our homes or to industries. 3. In a closed circuit, potential difference, current, and resistance are related; a change in any part of the circuit affects all other parts (almost) instantaneously. By using various electrical components in different arrangements, we are able to set up practical circuits to serve specific purposes. 4. Naturally occurring magnets, as well as man-made magnets, interact with other magnets or magnetic materials. A freely suspended magnet comes to rest pointing in the N-S direction due to its interaction with the Earth’s magnetic field. 5. Electricity and magnetism are related effects that have many applications in everyday life: moving charges (electric current) create magnetic fields; varying magnetic fields create electric fields (electromagnetic induction). 6. complex systems may also be better characterised by statistical averages (e.g. drift velocity, temperature) as these quantities may be more meaningful than the properties and behaviours of individual components (e.g. electron movement in a wire resulting in the current).

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