Download Solutions to Period 16 Exercises

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
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
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