CHAPTER 25 Flashcards
For electromagnetic induction to occur in
a circuit there must be a _________.
change in magnetic field intensity
When a magnet is quickly pushed into
a coil of wire connected to a circuit
_________.
work is needed to overcome a resistance
to the push
A magnet is rapidly plunged into a coil,
and then equally rapidly extracted. How
would you describe the voltages induced
in each case?
They will be of similar magnitude and
opposite sign.
What must change in order for electromagnetic induction to occur in a wire
coil?
The magnetic field through the coil must
change.
If the speed of the magnet is doubled, the
induced voltage is ________ .
twice as great
The same magnet is plunged into a coil
that has twice the number of turns as before, making it twice as long. The magnet
is shown before it enters the coil in . If
the speed of the magnet is again v, the
induced current in the coil is
unchanged
Faraday’s law states that induced voltage in a loop of wire depends upon the
rate at which _________.
a magnetic field in the loop changes
Electromagnetic induction occurs in a
loop of wire _________.
when there is relative motion of the loop
and wire or when current changes in the
loop when near a magnet
Increasing the number of loops of a coil
exposed to a changing magnetic field will
_________________.
increase the induced voltage
What are the three ways in which voltage
can be induced in a loop of wire?
Move a magnet near the loop, move the
loop near a magnet, change current in a
nearby loop
How does the frequency of induced voltage relate to how frequently one pole of a magnet is plunged in and out of a coil
of wire?
The frequencies are the same.
A common characteristic of motors
and generators is that they both
___________.
transform energy from one form into another
What are the basic differences and similarities between a generator and an electric motor?
In both, moving electrons experience a
force. The motor transforms electrical energy to mechanical energy. The generator transforms mechanical energy to
electrical energy.
Who discovered electromagnetic induction, and who put it to practical use?
Discovered by Faraday and Henry; put to
use by Tesla and Westinghouse
Is it correct to say that a generator produces energy? Defend your answer.
Generators do not produce energy. Instead, they convert it from some other
form to electrical energy.
What transforms from one coil to another
in a transformer is ___________.
power
If there are two times the number of
loops in the primary coil of a transformer
than in the secondary, what will the output voltage be with respect to the input
voltage?
The output voltage will be half.
What name is given to the rate at which
energy is transferred?
power
Which of these does a transformer
change: voltage, current, energy, power?
Voltage and current
How does the power input to an efficient
transformer compare with the power output?
Input power equals output power
