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18 Cards in this Set

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Q1. What is meant by "transformer action?"
A1. The transfer of energy from one circuit to another circuit by electromagnetic induction.
Q2. What are, the three basic parts of a transformer?
A2. Primary winding; secondary winding; core.
Q3. What are three materials commonly used as the core of a transformer?
A3. Air; soft iron; steel.
Q4. What are the two main types of cores used in transformers?
A4. Hollow-core type; shell-core type.
Q5. Which transformer windings are connected to an ac source voltage and to a load, respectively?
A5. Primary to source; secondary to load.
Q6. A transformer designed for high-voltage applications differs in construction in what way from a
transformer designed for low-voltage applications?
A6. Additional insulation is provided between the layers of windings in the high-voltage transformer.
Q8. What is meant by a "no-load condition" in a transformer circuit?
A8. A voltage is applied to the primary, but no load is connected to the secondary.
Q9. What is meant by "exciting current" in a transformer?
A9. Exciting current is the current that flows in the primary of a transformer with the secondary
open (no load attached).
Q10. What is the name of the emf generated in the primary that opposes the flow of current in the
primary?
A10. Self-induced or counter emf.
Q11. What causes a voltage to be developed across the secondary winding of a transformer?
A11. The magnetic lines generated by the current in the primary cut the secondary windings and
induce a voltage into them.
Q12. What is the phase relationship between the voltage induced in the secondary of an unlike-wound
transformer and the counter emf of the primary winding?
A12. In phase. Remember, the cemf of the primary is 180 degrees out of phase with the applied
voltage. The induced voltage of the secondary of an unlike-wound transformer is also 180
degrees out of phase with the primary voltage.
Q14. What is "leakage flux?"
A14. Lines of flux generated by one winding which do not link the other winding.
Q15. What effect does flux leakage in a transformer have on the coefficient of coupling (K) in the
transformer?
A15. It causes K to be less than unity (1).
Q23. Name the three power losses in a transformer.
A23. Copper loss, eddy-current loss, and hysteresis loss.
Q26. List five different types of transformers according to their applications.
a. Power transformer
b. Autotransformer
c. Impedance-matching transformer
d. Audio-frequency transformer
e. Radio-frequency transformer
Q28. What is the cause of most accidents?
A28. Carelessness.
Q29. Before working on electrical equipment containing capacitors, what should you do to the
capacitors?
A29. Discharge them by shorting them to ground.
Q30. When working on electrical equipment, why should you use only one hand?
A30. To minimize the possibility of providing a path for current through your body.