PHYS112 FINAL - RIO SALADO EXAM
QUESTIONS WITH COMPLETE
SOLUTIONS
When an iron bar is moved through a uniform magnetic field, what happens to the
charge carriers within the bar? - ANSWER-Negative charge carriers move relatively
freely while the positive charge carriers do not
How does the induced EMF in a conductor moving through a magnetic field affect
charge distribution? - ANSWER-It increases the charge separation
How is flux defined in the context of magnetic fields? - ANSWER-The measure of the
number of magnetic field lines passing through a given area
What doe Lenz's Law state regarding the direction of induced current? - ANSWER-The
induced current flows in the opposite direction of the changing flux
What does Faraday's Law state regarding the relationship between induced EMF and
the rate change of flux - ANSWER-The induced EMF is directly proportional to the rate
of change of flux
According to Faraday's law, what happens to the direction of the induced EMF with
respect to the change in flux? - ANSWER-It is opposite to the change in flux
In the context of Faraday's law, what does the negative sign in the equation signify? -
ANSWER-It signifies the direction of the induced EMF
What is the magnitude of the induced EMF across a metal bar (32cm) moved through a
0.30 T magnetic field and 23m/s? - ANSWER-Example work: BLvcos() = (0.30T)(0.32m)
(23m/s) = 2,208 = 2.2V
What is the fundamental difference between motors and generators? - ANSWER-
Motors convert electric energy into work, while generators convert work into electric
energy.
According to Faraday's law, what induces an EMF in a generator? - ANSWER-Change
in the angle between the loop and the magnetic field
According to. Faraday's law, what induces an EMF in a motor? - ANSWER-Change in
number of loops
, How does Lenz's law effect the operation of a generator? - ANSWER-It induces and
EMF that opposes the original current through the loop
How does Lenz's law effect the operation of a motor? - ANSWER-the EMF, opposes
any change, so that the input EMF that powers the motor will be opposed by the motor's
self-generated EMF, called the back EMF of the motor.
What is the purpose of a transformer in an electrical circuit? - ANSWER-To change the
voltage in a circuit
What did Maxwell's electromagnetic theory demonstrate? - ANSWER-The wave nature
of electricity and magnetism
Which equation describes the nature and behavior of magnetic field lines? - ANSWER-
Grauss's Law of magnetism
What does Ampere's circuit law describe? - ANSWER-how magnetic fields are created
by moving charges or changing electric fields
How are electric and magnetic waves related according to Maxwell's equation? -
ANSWER-They occur together and travel perpendicular to each other
What is the relationship between the speed and on EM wave and the amplitude of the
electric and magnetic fields? - ANSWER-Speed is directly proportional to the amplitude
of the electric field
What property of waves does wavelength measure - ANSWER-the distance between
crests
What is the SI unit for frequency? - ANSWER-Hertz (Hz)
If a wave has a frequency of 6.7x10^14 Hz, what is its wavelength? - ANSWER-
c=(wavelength)(f) -> 3x10^8 = (x)(6.7x10^14) -> x = (3x10^8)/(6.7x10^14) = 4.5x10^-7
What is the relationship between the energy of an electromagnetic wave and the
amplitude of its electric or magnetic field? - ANSWER-The energy is proportional to the
square of the amplitude.
What are the SI units of intensity? - ANSWER-Watts per meter squared (W/m^2)
What are the SI units for wavelength? - ANSWER-meter (m)
What is the purpose of a transformer? - ANSWER-Transformers change the voltage in a
circuit
QUESTIONS WITH COMPLETE
SOLUTIONS
When an iron bar is moved through a uniform magnetic field, what happens to the
charge carriers within the bar? - ANSWER-Negative charge carriers move relatively
freely while the positive charge carriers do not
How does the induced EMF in a conductor moving through a magnetic field affect
charge distribution? - ANSWER-It increases the charge separation
How is flux defined in the context of magnetic fields? - ANSWER-The measure of the
number of magnetic field lines passing through a given area
What doe Lenz's Law state regarding the direction of induced current? - ANSWER-The
induced current flows in the opposite direction of the changing flux
What does Faraday's Law state regarding the relationship between induced EMF and
the rate change of flux - ANSWER-The induced EMF is directly proportional to the rate
of change of flux
According to Faraday's law, what happens to the direction of the induced EMF with
respect to the change in flux? - ANSWER-It is opposite to the change in flux
In the context of Faraday's law, what does the negative sign in the equation signify? -
ANSWER-It signifies the direction of the induced EMF
What is the magnitude of the induced EMF across a metal bar (32cm) moved through a
0.30 T magnetic field and 23m/s? - ANSWER-Example work: BLvcos() = (0.30T)(0.32m)
(23m/s) = 2,208 = 2.2V
What is the fundamental difference between motors and generators? - ANSWER-
Motors convert electric energy into work, while generators convert work into electric
energy.
According to Faraday's law, what induces an EMF in a generator? - ANSWER-Change
in the angle between the loop and the magnetic field
According to. Faraday's law, what induces an EMF in a motor? - ANSWER-Change in
number of loops
, How does Lenz's law effect the operation of a generator? - ANSWER-It induces and
EMF that opposes the original current through the loop
How does Lenz's law effect the operation of a motor? - ANSWER-the EMF, opposes
any change, so that the input EMF that powers the motor will be opposed by the motor's
self-generated EMF, called the back EMF of the motor.
What is the purpose of a transformer in an electrical circuit? - ANSWER-To change the
voltage in a circuit
What did Maxwell's electromagnetic theory demonstrate? - ANSWER-The wave nature
of electricity and magnetism
Which equation describes the nature and behavior of magnetic field lines? - ANSWER-
Grauss's Law of magnetism
What does Ampere's circuit law describe? - ANSWER-how magnetic fields are created
by moving charges or changing electric fields
How are electric and magnetic waves related according to Maxwell's equation? -
ANSWER-They occur together and travel perpendicular to each other
What is the relationship between the speed and on EM wave and the amplitude of the
electric and magnetic fields? - ANSWER-Speed is directly proportional to the amplitude
of the electric field
What property of waves does wavelength measure - ANSWER-the distance between
crests
What is the SI unit for frequency? - ANSWER-Hertz (Hz)
If a wave has a frequency of 6.7x10^14 Hz, what is its wavelength? - ANSWER-
c=(wavelength)(f) -> 3x10^8 = (x)(6.7x10^14) -> x = (3x10^8)/(6.7x10^14) = 4.5x10^-7
What is the relationship between the energy of an electromagnetic wave and the
amplitude of its electric or magnetic field? - ANSWER-The energy is proportional to the
square of the amplitude.
What are the SI units of intensity? - ANSWER-Watts per meter squared (W/m^2)
What are the SI units for wavelength? - ANSWER-meter (m)
What is the purpose of a transformer? - ANSWER-Transformers change the voltage in a
circuit
