Transformers Y 11

Primary Coil of a transformer is determined by _________.

• which coil has more turns

• which coil is nearer to the load

• which coil is connected to the source

• which side has the highest voltage

What type of transformer is used to increase the voltage from power stations.

• Step-down transformer

• Step-up transformer

Why transformers work with A.C. current but not D.C.

• A.C current produces changing magnetic field.

• D.C current produces changing magnetic field.

• D.C current is weak

• A.C current is powerful

Which of the following does not change in a transformer?

• Voltage

• Current

• Power

This picture is an example of a ________________.

• Motor

• Generator

• Step-up transformer

• Step-down transformer

Ratio of voltages is equal to ratio of _______________________.

• number of iron sheets in core

• number of coil

• number of turns in coil

• number of electromagnetic

A transformer has 100 turns in the primary coil and 25 turns in the secondary coil. When a 120 V is applied to the primary coil, what is the voltage in the secondary coil?

• 480V

• 30V

• 20V

• 450V

The function of a transformer is to ...

• raise and lower the apparent power levels

• transfer DC voltage from the primary winding to the secondary winding

• increase or decrease A.C voltage or A.C current levels

• transform mechanical energy into electrical energy

A step up transformer has its primary number of turns to secondary number of turns ratio

• Greater than 1

• Equal to 1

• Less than 1

• Unknown

Insulators are put between core lamination ...

• to prevent flux leaks to the neighboring steel sheet

• to reduce the cross-sectional area of the core

• to prevent short circuit in the transformer

• to prevent rusting in the lamination