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Electromagnetism 1 a) The figure below shows a horizontal wire which is at right angles to a magnetic field. The magnetic field is produced by a horseshoe magnet which is on balance adjusted to read zero when the current in the wire is zero. When the current is 4 A, the reading on the balance is 0.8 g. The length of wire in the magnetic field is 0.05 m. Calculate the average magnetic flux density along the length of the wire. (4 marks) Length of wire in field. Magnet Balance 0.8 b) A rectangular coil ABCD contains 220 turns of wire and is placed between the poles of a magnet. The coil can rotate about an axis through its centre. When the current through the coil is 110 mA, the maximum moment or torque produced in the coil is 1.7 x 10-³ N m. P magret D i) The plane of the coil is parallel to the magnetic field in the figure above. Calculate the magnitude of the force on side AB of the coil. (2 marks) ii) Use your answer for i) to calculate the magnetic flux density B of the magnet. marks) (2)