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Per16_exercise

# Per16_exercise - side of the rotor e NONE of the answers is...

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Solutions to Period 16 Exercises E.1 To operate, a motor must a) have at least one changing magnetic field. b) have at least two changing magnetic fields. c) have one fixed magnetic field and one changing magnetic field. d) have none of the above. E.1 = a E.2 You wish to design an electric motor. Which of the following motor designs will NOT work? a) An electromagnet is used to spin a permanent magnet. b) A permanent magnet is used to spin an electromagnet. c) A permanent magnet is used to spin a permanent magnet. d) An electromagnet is used to spin an electromagnet. e) An electric motor can be made from all of the above designs. Since you need at least one changing magnetic field, two permanent magnets do not work. E.2 = c 16-Ex 1&2

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E.3 The rotor of the St. Louis motor used in class turns because a) there is a repulsive force between like charges on the rotor coils. b) energy is conserved in an electric motor. c) there is a magnetic force between the rotor coils and the permanent magnets. d) gravity exerts a greater force on one

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Unformatted text preview: side of the rotor. e) NONE of the answers is correct. E.3 = c 16-Ex 3 E.4 Which of the following best describes the purpose of a commutator in an electric motor operating on direct current? a) to change linear motion into rotating motion b) to change alternating current into direct current c) to change a magnetic field into an electrostatic field d) to produce a changing current through a coil of wire e) to change mechanical energy of motion into thermal energy A changing current produces the changing magnetic field required in a motor. E.4 = d 16-Ex 4 E.5 Which of the following are features of a universal AC motor? a) one or more permanent magnets b) a commutator c) electromagnets d) Both b) and c) are features of a universal motor. e) All of the above are features of a universal motor. E.5 = d 16-Ex 5 Solutions to Period 16 Exercises E.1 = a E.2 = c E.3 = c E.4 = d E.5 = d...
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