A step-down transformer is used for recharging the batteries of portable devices

Question

A step-down transformer is used for recharging the batteries of portable devices. The turns ratio N2/N1 for a particular transformer used in a CD player is 7:30. When used with 120 V (rms) household service, the transformer draws an rms current of 100 mA. Find the following. rms output voltage of the transformer V power delivered to the CD player Your response differs from the correct answer by 10% to 100%. W Need Help? A speeder tries to explain to the police that the yellow warning lights on the side of the road looked green to her because of the Doppler shift. How fast would she have been traveling if yellow light of wavelength 572 nm had been shifted to green with a wavelength of 555 nm? (Note: For speeds less than 0.03c, the equation below will lead to a value for the change of frequency accurate to approximately two significant digits. Accordingly, please enter your response to 2 significant digits.) speed = Your response is within 10% of the correct value. This may be due to roundoff error, or you could have a mistake in your calculation. Carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. m/s Need Help?

Explanation / Answer

    for an ideal transformer the average power input= average power output     (Pav)input =(Pav)output     (Pav)input = (28 V) (100mA)                    = (28 V) (0.100 A)                    = ....... W

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