2-2-3 Introduction to Transformers

Question 1

The largest advantage AC has over DC is that it can be transformed from one voltage to another.

Answer 1

True

Question 2

Ohm’s law cannot be used directly on AC circuits because __?__.

Answer 2

reactance and resistance oppose current flow

Question 3

Impedance is the combination of resistance and current.

Answer 3

False

Question 4

All transformer connections, single and three-phase, are based on the voltage and current rules for __?__ and __?__ circuits.

Answer 4

series / parallel

Question 5

AC at 60 hertz per second increases and decreases in value __?__ times per second.

Answer 5

120

Question 6

The magnetic field surrounding a coil rises and falls in unison with the current.

Answer 6

True

Question 7

Voltage is induced in the secondary coil of a transformer by electromagnetic induction.

Answer 7

True

Question 8

To obtain maximum induction, the coils must be __?__ and __?__ so the field is able to cut across the conductors of the other.

Answer 8

parallel / sufficiently close

Question 9

The magnetic field must be __?__ in order to induce a voltage and cause a current to flow in the circuit.

Answer 9

in motion

Question 10

In order for current to flow, the conductor must be a closed circuit.

Answer 10

True

Question 11

The __?__ concentrates and directs the magnetic field and makes transformers possible.

Answer 11

iron core

Question 12

Laminating an iron core directs the maximum amount of magnetic flux lengthways in the iron core.

Answer 12

True

Question 13

Adding more turns to a coil __?__ the magnetic effect.

Answer 13

increases

Question 14

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.

Answer 14

False

Question 15

Of the three things which govern the strength of a transformers electromagnetic field, the amount of current flowing and the __?__ are two of them.

Answer 15

number of turns in the winding

Question 16

The primary of a transformer designates the winding that is supplied with electricity.

Answer 16

True

Question 17

The primary coil of a transformer is always a high voltage winding.

Answer 17

False

Question 18

A transformer may be either a __?__ or a __?__, depending on its use.

Answer 18

step up / step down

Question 19

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.

Answer 19

True

Question 20

Using Ohm’s law, when reducing voltage through a transformer the __?__ to supply the load.

Answer 20

current will increase

Question 21

A power plant transformer __?__ the voltage and __?__ the current on a transmission line.

Answer 21

increases / reduces

Question 22

Since transformers have no moving parts, their efficiency is always 100%.

Answer 22

False