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Electromagnetism 1 a) Sketch the magnetic fields due to the following on separate diagrams: i) A long, thin conductor carrying a constant current / ii) A solenoid of n turns carrying a constant current / and iii) A bar magnet lying vertically on the page with the south pole at the bottom. (3 marks) [Note: you should indicate the direction of any vector quantities.) b) Calculate the magnetic field strength in the centre of a solenoid with 10 turns per cm, carrying a current of 1.3 A (uo = 410 x 10-7 NA 2). (2 marks) c) A current carrying wire can be made to 'float' in a magnetic field if the force on the wire, due to the magnetic field, balances the wire's weight. What is the minimum magnetic field strength required to balance a wire which has a mass per unit length of 52.4 g m-1 and which is carrying a current of 17 A? (3 marks)