CEA Transformers and Distribution Systems

Question 1

What is the turns ratio of a transformer with a primary winding of 480 turns and a secondary winding of 120 turns?

Accepted Answer

4:1

Answer

The turns ratio is calculated by dividing primary turns by secondary turns: 480 ÷ 120 = 4:1.

Question 2

A step-down transformer has a 2:1 turns ratio and a primary voltage of 240V. What is the secondary voltage?

Accepted Answer

120V

Answer

With a 2:1 turns ratio, the secondary voltage is half the primary: 240V ÷ 2 = 120V.

Question 3

What operating principle allows a transformer to transfer electrical energy between two circuits?

Accepted Answer

Mutual electromagnetic induction

Answer

Transformers operate on mutual electromagnetic induction, where a changing magnetic field in the primary winding induces a voltage in the secondary winding.

Question 4

Which transformer type has its secondary winding electrically isolated from the primary winding with no common connection?

Accepted Answer

Isolation transformer

Answer

An isolation transformer has separate primary and secondary windings with no electrical connection between them, providing complete electrical isolation.

Question 5

If an ideal transformer draws 5A at 240V on the primary, what is the secondary current when the secondary voltage is 120V?

Accepted Answer

10A

Answer

In an ideal transformer, primary VA equals secondary VA: 240V × 5A = 120V × I, solving gives I = 10A.

(CEA) Certified Electrical Apprentice Practice Test

(CEA) Certified Electrical Apprentice Practice Test

CEA Transformers and Distribution Systems