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Electronics - Transformers

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Exercise

"Actions speak louder than words."
- (Proverb)
1.

When does maximum power transfer happen from the source to the load?

 A. When the source resistance is greater than the load resistance B. When the source resistance is less than the load resistance C. When there is negligible source resistance D. When the source resistance equals the load resistance

2.

A transformer is plugged into a 120 V rms source and has a primary current of 300 mA rms. The secondary is providing 18 V across a 10 load. What is the efficiency of the transformer?

 A. 88% B. 90% C. 92% D. 95%

3.

The coefficient of coupling between two coils is 0.45. The first coil has an inductance of 75 mH and the second coil has an inductance of 105 mH. What is the mutual inductance between the coils?

 A. 3.54 mH B. 7.88 mH C. 39.9 mH D. 189.3 mH

4.

Increasing the number of turns of wire on the secondary of a transformer will

 A. increase the secondary current B. decrease the secondary current C. have no effect on the secondary current D. increase the primary current

5.

What is the turns ratio of the transformer needed to match a 1 k source resistance to a 160 load?

 A. 2.5:1 B. 0.4:1 C. 6.25:1 D. 16:1