Transformers

A transformer is ...

• a rotating machine

• an electromechanical energy converter

• an electromagnetic machine

• AC-DC machine

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 winding to secondary winding ratio

• Greater than 1

• Equal to 1

• Less than 1

• Unknown

Primary winding of a transformer is determined by ...

• which winding is nearer to the load

• which winding is connected to the source

• which winding has more turns

• which side has the highest voltage

The electrical energy is transferred through the ... in a transformer.

• electric field

• rotor

• air space

• magnetic field

Choose the correct statement:

• The ratio of the secondary voltage to the primary voltage is equal to the ratio of the primary turn to the secondary turn

• The ratio of the primary current to the secondary current is equal to the ratio of the primary voltage to the secondary voltage

• The ratio of the primary apparent power to the secondary apparent power is equal to the ration of the primary voltage to the secondary voltage

• The ratio of the secondary current to the primary current is equal to the ratio of the primary turn to the secondary turn

Mutual induction means: (Choose the correct statement)

• A conductor (wire) placed in a varying magnetic field will have a current induced in it

• A conductor produces varying magnetic field

• Two conductors must be connected together to produce current

• Two conductors cannot used magnetic field to produce current

Metal core in a transformer is used to:

• provide current path and reduce losses

• Reduce the losses and provide magnetic field path

• to provide electrical connection between primary and secondary

• There is no significance of using the core

choose all step down transformers

• TV adapter

• Mobile charger

• Transformer outside the homes

• Transformers outside power generating stations

Assume primary has 240 turns and secondary has 60 turns. Primary is connected with 120V AC power supply. What is the voltage on the secondary?

• 30 V

• 0.333 V

• 2 V

• 120V