4.1 Simple phenomena of magnetism

• State the properties of magnets

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• Give an account of induced magnetism

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• Distinguish between ferrous and non-ferrous materials

• Describe methods of magnetisation and of demagnetisation

• Describe an experiment to identify the pattern of field lines round a bar magnet

• Distinguish between the magnetic properties of iron and steel

• Distinguish between the design and use of permanent magnets and electromagnets

4.5 Electromagnetic effects

4.5 (a) Electromagnetic induction

• Describe an experiment that shows that a changing magnetic field can induce an e.m.f. in a circuit

• State the factors affecting the magnitude of an induced e.m.f.

• Show understanding that the direction of an induced e.m.f. opposes the change causing it

4.5 (b) a.c. generator

• Describe a rotating-coil generator and the use of slip rings

• Sketch a graph of voltage output against time for a simple a.c. generator

4.5 (c) Transformer

• Describe the construction of a basic iron-cored transformer as used for voltage transformations

• Describe the principle of operation of a transformer

• Recall and use the equation (Vp /Vs) = (Np /Ns)

• Recall and use the equation Vp Ip = Vs Is (for 100% efficiency)

• Describe the use of the transformer in high voltage transmission of electricity

• Give the advantages of high-voltage transmission

• Explain why energy losses in cables are lower when the voltage is high

4.5 (d) The magnetic effect of a current

• Describe the pattern of the magnetic field due to currents in straight wires and in solenoids

• State the qualitative variation of the strength of the magnetic field over salient parts of the pattern

• Describe the effect on the magnetic field of changing the magnitude and direction of the current

• Describe applications of the magnetic effect of current, including the action of a relay

4.5 (e) Force on a current-carrying conductor

• Describe an experiment to show that a force acts on a current-carrying conductor in a magnetic field, including the effect of reversing:

(i) the current (ii) the direction of the field

• Describe an experiment to show the corresponding force on beams of charged particles

• State and use the relative directions of force, field and current

4.5 (f) d.c. motor

• State that a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing the number of turns on the coil

• Describe the effect of increasing the current

• Relate this turning effect to the action of an electric motor

4.6 Cathode-ray oscilloscopes

4.6 (a) Cathode rays

• Describe the production and detection of cathode rays

• Describe their deflection in electric fields

• State that the particles emitted in thermionic emission are electrons

4.6 (b) Simple treatment of cathode-ray oscilloscope

• Describe (in outline) the basic structure and action of a cathode-ray oscilloscope (detailed circuits are not required)

• Use and describe the use of a cathode-ray oscilloscope to display waveforms