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 3:49. When used with 120-V (rms) household service, the transformer draws an rms current of 180 mA (a) Find the rms output voltage of the transformer. .35 (b) Find the power delivered to the CD player. 22.2 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. W Need Help?Read it 10. 1/2 points | Previous Answers SerCP11 21.P049 My Notes Ask Your Teacher The U.S. Navy has long proposed the construction of extremely low frequency (ELF waves) communications systems; such waves could penetrate the oceans to reach distant submarines. Calculate the length of a quarter-wavelength antenna for a transmitter generating ELF waves of frequency 84 Hz. 915 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 al intermediate results to at least four-digit accuracy to minimize roundoff error. km

Explanation / Answer

Q9.

part a)

In a step down transformer

V2 = V1*N2/N1

V2 = 120*3/49

V2 = 7.35 V

Part b)

Power input = power output

V1*I1 = V2*I2
P = 120*0.180

P = 21.6 W

Q10.

= Wavelength in meters
f = frequency in Hz
= c/f

= 3x108/84

= 3571428.5714 m
/4 =892.8571428 km

/4 =893 km

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