1. A transformer for an answering machine takes an AC voltageof 170 V. (maximum,
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1. A transformer for an answering machine takes an AC voltageof 170 V. (maximum, or peak-to-peak) as its input and provides 7.8V (rms) as its output to the answering machine. A) What is the rms equivalent to this peak-to-peakvoltage? B) Calculate the turns ratio between the primary andsecondary. C) When not answering, the machine uses a maximum power of 5.0W. What is the current (rms) drawn from the 170 V line? 2. An astronomer is making an observation of a new-discoveredgalactic object. Part of this observation is the analsis of thelight emitted by the object. It is observed that this lightincludes a clear pattern of the emission spectrum of atomichydrogen. Part of that spectrum is the H line, which on earth hasa wavelength of 656.258 nm (10-9m). The observed light from this object hasthis spectral line measured at 659.0 nm. Explain this discrepancy, quantitatively, using the DopplerEffect. thank you. Please help me. 1. A transformer for an answering machine takes an AC voltageof 170 V. (maximum, or peak-to-peak) as its input and provides 7.8V (rms) as its output to the answering machine. A) What is the rms equivalent to this peak-to-peakvoltage? B) Calculate the turns ratio between the primary andsecondary. C) When not answering, the machine uses a maximum power of 5.0W. What is the current (rms) drawn from the 170 V line? 2. An astronomer is making an observation of a new-discoveredgalactic object. Part of this observation is the analsis of thelight emitted by the object. It is observed that this lightincludes a clear pattern of the emission spectrum of atomichydrogen. Part of that spectrum is the H line, which on earth hasa wavelength of 656.258 nm (10-9m). The observed light from this object hasthis spectral line measured at 659.0 nm. Explain this discrepancy, quantitatively, using the DopplerEffect. thank you. Please help me.Explanation / Answer
1. A. The rms voltage equivalent to this peak voltage is 170/2= 120.2 V B. The turns ratio: Ni/No =Vi/Vo = 120.2 / 7.8 = 15.41 C. The current draw from the primary 170V line: I = P/V = 5/120.2 = 0.042 A 2. The discrepancy is caused by the relative motion of the source andthe observer. Assume the observer and the source are moving away from each otherwith a relative velocity v. We use the relativisitc Doppler effect: s: source o: observed fs/fo = o/s= ((1+)/(1-)) = 659/656.258 = k (1+)/(1-) = k2 1+ = k2 - k2 + k2 = k2-1 = (k2-1)/(k2+1) = 4.17E-3 = v/c v = c = 1.25E6 m/s
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