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Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 16: Electromagnetic Induction 16-1 H2 Topic 16 Electromagnetic Induction Pickup of an electric guitar A moving coil speaker cone

Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 16: Electromagnetic Induction 16-2 Learning Objectives Content  Magnetic Flux  Laws of Electromagnetic Induction Learning Outcomes Candidates should be able to a. define magnetic flux and the weber. b. recall and solve problems using  = BA. c. define magnetic flux linkage. d. infer from appropriate experiments on electromagnetic induction: i. that a changing magnetic flux can induce an e.m.f. in a circuit, ii. that the direction of the induced e.m.f. opposes the change producing it, iii. the factors affecting the magnitude of the induced e.m.f. e. recall and solve problems using Faraday’s law of electromagnetic induction and Lenz’s law. f. explain simple applications of electromagnetic induction.

Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 16: Electromagnetic Induction 16-3 16.0 Introduction In Topic 15, you learnt two ways in which electricity and magnetism are related: i. an electric current produces a magnetic field ii. a magnetic field exerts a force on an electric current or moving electric charge. 16.1 Magnetic Flux Field lines tell us the strength and direction of the magnetic field. However, there are times where we will need to be able to calculate the amount of magnetic field that passes through a surface area. Hence, magnetic flux is the term used, and it is a measure of the number of field lines that pass through a given area A. Magnetic Flux passing through any surface area is defined as The product of the magnetic flux density and the area normal to the f ield through which the field is passing. For a uniform magnetic flux density B at an angle θ to an area A, the magnetic flux is given by Alternatively, we can view magnetic flux as the product of the component of B perpendicular to the surface and the area of the surface. ( ) Weber The SI unit of magnetic flux is the weber (symbol: Wb) which i s defined as the magnetic flux if a uniform magnetic flux density of 1 tesla passes perpendicularly through an area of 1 m2. (1 Wb = 1 T m2) 16.1.1 Magnetic Flux Linkage If the area A is bounded by a coil and the coil has N turns, then the total magnetic flux passing through the coil, otherwise known as magnetic flux linkage through the coil, is From the equation, magnetic flux linkage through a coil depends on i. number of turns in the coil N ii. magnitude of magnetic flux density B iii. the surface area A iv. the orientation of the coil  with respect to the direction of B. (Note:  is the angle