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Unformatted text preview: Example Problems: Chapter 21 Q1: A step-down transformer is used for recharging the batteries of portable devices such as tape players. The turns ratio inside the transformer is 13:1 and it is used with 120 V (rms) household service. If a particular ideal transformer draws 0.350 A from the house outlet, what are (a) the voltage and (b) the current supplied to a tape player from the transformer? (c) How much power is delivered? A: (a) ( 29 ( 29 2 2,rm s 1,rm s 1 1 120 V 13 N V V N = = = 9.23 V (b) For an ideal transformer, ( 29 ( 29 2,rm s 2,rm s 1,rm s 1,rm s V I V I = so ( 29 1,rm s 1 2,rm s 1,rm s 1,rm s 2,rm s 2 13 0.350 A 1 V N I I I V N = = = = 4.55 A (c) ( 29 ( 29( 29 av 2,rm s 2,rm s 9.23 V 4.55 A V I = = = 42.0 W Q2: A step-up transformer is designed to have an output voltage of 2 200 V (rms) when the primary is connected across a 110-V (rms) source. (a) If there are 80 turns on the primary winding, how many turns are required on the secondary? a 110-V (rms) source....
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- Summer '08