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Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 15: Electromagnetism 15-1 H2 Topic 15 Electromagnetism Magnetic field lines showed by iron fillings An exploded view of an electric motor Large Hadron Collider (LHC) Tunnel: A 17 mile long tunnel underlying the border between Switzerland and France

Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 15: Electromagnetism 15-2 Learning Objectives Content  Force on a current-carrying conductor  Force on a moving charge  Magnetic fields due to currents  Force between current-carrying conductors Learning Outcomes Candidates should be able to a. Show an appreciation that a force might act on a current -carrying conductor placed in a magnetic field. b. Recall and solve problems by using the equation F = BIL sin θ, with directions as interpreted by Fleming's left-hand rule. c. Define magnetic flux density and the tesla. d. Show an understanding of how the force on a current -carrying conductor can be used to measure the flux density of a magnetic field, using a current balance. e. Predict the direction of the force on a charge moving in a magnetic field. f. Recall and solve problems by using F = B q v sin θ. g. Describe and analyse deflections of beams of charged particles by uniform electric and uniform magnetic fields. h. Explain how electric and magnetic fields can be used in velocity selection for charged particles. i. Sketch flux patterns due to a long straight wire, a flat circular coil and a long solenoid. j. Show an understanding that the field due to a solenoid may be influenced by the presence of a ferrous core. k. Explain the forces between current -carrying conductors and predict the directions of the forces.

Dunman High School (Senior High Physics Department) 9646 Physics (2014) Topic 15: Electromagnetism 15-3 15.1 Magnetic Fields Besides the gravitational field and the electric field, another field of force in nature is the magnetic field. A magnetic field is a region of space where a magnetic pole, a current-carrying conductor or a moving charge particle will experience a force. A magnetic field can be produced by: (i) Permanent magnets (ii) Current-carrying conductors The magnetic field around a permanent magnet can be seen by sprinkling some iron filings around it. In 1820, the Danish physicist, Hans Christian Oersted first discovered that magnetic fields are produced by electric currents. It is the motion of the electric charge in the conductor that produces the magnetic field. 15.1.1 Magnetic Field Lines A magnetic field may be re presented by a series of lines called magnetic field lines, each having a specific direction. The direction of a magnetic field line at any point in the field shows the direction of the force that a ‘free’ magnetic north pole would experience at that point. The fo