2-2-3 Introduction to Transformers Flashcards
The largest advantage AC has over DC is that it can be transformed from one voltage to another.
True
Ohm’s law cannot be used directly on AC circuits because __?__.
reactance and resistance oppose current flow
Impedance is the combination of resistance and current.
False
All transformer connections, single and three-phase, are based on the voltage and current rules for __?__ and __?__ circuits.
series / parallel
AC at 60 hertz per second increases and decreases in value __?__ times per second.
120
The magnetic field surrounding a coil rises and falls in unison with the current.
True
Voltage is induced in the secondary coil of a transformer by electromagnetic induction.
True
To obtain maximum induction, the coils must be __?__ and __?__ so the field is able to cut across the conductors of the other.
parallel / sufficiently close
The magnetic field must be __?__ in order to induce a voltage and cause a current to flow in the circuit.
in motion
In order for current to flow, the conductor must be a closed circuit.
True
The __?__ concentrates and directs the magnetic field and makes transformers possible.
iron core
Laminating an iron core directs the maximum amount of magnetic flux lengthways in the iron core.
True
Adding more turns to a coil __?__ the magnetic effect.
increases
Of the three things which govern the strength of a transformer’s electromagnetic field, the ease with which the core can be magnetized is not one of them.
False
Of the three things which govern the strength of a transformers electromagnetic field, the amount of current flowing and the __?__ are two of them.
number of turns in the winding
The primary of a transformer designates the winding that is supplied with electricity.
True
The primary coil of a transformer is always a high voltage winding.
False
A transformer may be either a __?__ or a __?__, depending on its use.
step up / step down
The kVA that is being drawn off of a transformer can be found by multiplying secondary voltage times secondary amperage and dividing the result by one thousand.
True
Using Ohm’s law, when reducing voltage through a transformer the __?__ to supply the load.
current will increase
A power plant transformer __?__ the voltage and __?__ the current on a transmission line.
increases / reduces
Since transformers have no moving parts, their efficiency is always 100%.
False
