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U.S. GOVERNMENT PRINTING OFFICE; 1949
CHAPTER 4 QUIZ
ELECTRICITY FROM MAGNETISM
NOTICE: This page has not been proofed yet!
1. Who discovered electromagnetic induction?
2. Complete the following statements:
(a) The principle of electromagnetic induction states that when a conductor is moved across a
magnetic field an electromotive force (emf) is in the conductor.
(b) Faraday fOlmd that when a
conductor is moved across a magnetic field
(1) The faster the conductor moves the the emf.
(2) Reversing the movement of the conductor _ the emf.
(3) If the conductor is
stationary the emf is h •
(c) Whenever there is relative between a conductor and a magnetic field
induction takes place.
3. Complete the following:
(a) To indicate the direction of induced emf hold the left hand so
(1) The first finger points in the direction of h •
(2) The thumb points in the
direction of hhh'
(3) the middle finger will point in the direction of
(b) To reverse
the direction of the induced emf you must reverse the direction of either (1) conductor - _ h __ or (2) magnetic .
(c) The left hand rule for direction of induced emf will help you determine the direction of hh __ produced
in a generator.
4. Complete the following statements:
(a) The more flux lines a conductor cuts
each second the _ n is the induced emf.
(b) 100,000,000 flux lines must be cut by a single conductor
each second to produce one _ n n _. c' To cut more lines per second you must
(1) increase the n
of the conductor.
(2) increase the strength of the .
(3) use more in each coil of
the armature. "
5. Complete the following statements:
(a) A voltage is induced in a conductor when the magnetic field
around it is _nn_.
(b) When a voltage is induced in one circuit by change of current in another.
(1) the circuit in which the current is changing IS called the n'
(2) The circuit in
which the voltage is induced IS called the n n __ . ~ is /'
(c) Production of an emf in one circuit by
change of current in another is called mutual .
(d) The circuit in which the current is changing gets
its energy from a· battery or .
(e) The circuit in which a voltage is induced gets its energy from the _
n of the other circuit.
(f) Induction by movement of a conductor underlies the operation of n n __ .
(g) Induction by flux linkage of one circuit to another underlies the operation of . ~.
6. Complete the following statements:
(a) An induced current, like the current produced by a
battery, creates a magnetic n __ around the conductor. - You know from Faraday's laws that:
When you move a conductor across a magnetic field you generate an induced emf in the conductor.
(2) The induced emf sets up an induced current in the conductor.
(3) The induced
current sets up a magnetic field around the conductor.
7. Using this information complete the following
(a) Lenz's law states that this magnetic field will be in direction to the conductor motion
that is creating the induced emf.
(b) Lenz's law means that the more power output yo get from a
generator, the the prime move:! must work to drive it.
8. Complete the following statements:
Flux produced by one turn of a current-carrying coil cutting another turn, produces a voltage of _ induction.
(b) Any coil carrying a current will induce a voltage in itself whenever its current .
the current is increasing, this induced emf will ___ ~ __ the current flow.
(d) When the current is
decreasing this induced emf will ______ the current flow.
(e) In self induction the induced emf any
changes ill the current value.
9. The self induced voltage in a generator field helps current flow across
the switch in the field circuit when this switch IS
10. Resistors are connected across the switch for the
field circuit of a generator to prevent burning of the switch when it is .
CHAPTER 4 ANSWERS
1. Stay tuned