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Unformatted text preview: Physics 21 Fall 2007 Solution to HW23 Transformers Consider the transformer ideal unless otherwise noted. (A) The primary coil of a transformer contains 100 turns; the secondary has 200 turns. The primary coil is connected to a size AA battery that supplies a constant voltage of 1.5 volts. What vol tage would be measured across the secondary coil? ( multiple choice: the correct answer is zero since the AA battery is dc ) (B) A transformer is intended to decrease the rms value of the alterna ting voltage from 500 volts to 25 volts. The primary coil contains 200 turns. Find the necessary number of turns N _2 in the secon dary coil. 500/25 = N _P/ N _S = 200/ N _S => N _S = 10 (C) A trans former is intended to decrease the rms value of the alternating current from 500 amperes to 25 amperes. The primary coil con tains 200 turns. Find the necessary number of turns N _2 in the secondary coil. Power = I V is constant. Current decreases by 500A/25A = 20, so N must go up by 20. 20 x 200 = N _2 = 4000 (D) In a transformer, the primary coil contains 400 turns, and the secondary coil contains 80 turns. If the primary current is 2.5 amperes, what is the secondary current I_2? amperes, what is the secondary current I_2?...
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 Spring '08
 Hickman
 Physics

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