## transformers

###### What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?
 A 4 kVA B 0.25 kVA C 16 kVA D 8 kVA
 ANS: C - 16 kVA

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###### The turns ratio required to match an 80  source to a 320  load is
 A 80 B 20 C 4 D 2
 ANS: D - 2

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###### When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is
 A 12 V B 120 V C 240 V D 2,400 V
 ANS: C - 240 V

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###### If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250
 A 250 B 25 C 6,250 D 62,500
 ANS: D - 62,500

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###### A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is
 A 0.2 B 0.4 C 5 D 25
 ANS: C - 5

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###### The primary winding of a transformer has 110 V ac across it. What is the secondary voltage if the turns ratio is 8?
 A 8.8 V B 88 V C 880 V D 8,800 V
 ANS: C - 880 V

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###### To step 110 V ac down to 20 V ac, the turns ratio must be
 A 5.5 B 18 C 0.18 D 0.018
 ANS: C - 0.18

Vp/Vs = Np/Ns

Vs = (Ns/Np)Vp

We required turns ratio i.e., (Ns/Np)

= Vs/Vp

= 20/110

= 0.181818182

###### The mutual inductance when k = 0.65, L1 = 2 H, and L2 = 5 H is
 A 2 mH B 2 H C 4 H D 8 H
 ANS: B - 2 H

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###### A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, RL, is 120 . What is the approximate voltage across the load?
 A 7.3 V B 73 V C 88 V D 880 V
 ANS: A - 7.3 V

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