Physics Principles and Problems 2009

Section 25.2 : Changing Magnetic Fields Induce EMF

Self-Check Quizzes

1
When a motor is turned on there is an initial large current that decreases after the motor begins to turn due to the _____.
A)back-EMF
B)magnetic field
C)resistance in the motor
D)induced current
2
What is required to produce an eddy current in a piece of aluminum?
A)a power source
B)a magnetic field
C)a current-carrying wire
D)a back-EMF
3
If the current in a coil reaches a constant value, the EMF _____.
A)increases
B)decreases
C)is zero
D)acts to oppose the magnetic field
4
If Np < Ns, what device is being described?
  Need a Hint?
A)a DC generator
B)a step-down transformer
C)an AC generator
D)a step-up transformer
5
Why are high voltages used for long-distance transmission of electrical energy?
A)to keep the energy loss low
B)higher voltages can travel further
C)so that the energy can be evenly distributed
D)so the voltage can be measured easily
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