1. The amount of useful output power provided by a device is 1.5 W. It is powered by a 48-V supply with 100 mA of current. How much power is wasted in heat?

answer: 3.3 W

2. What is the peak voltage of a sine wave that measures 220 VAC rms?

answer: 311 VAC

3. A 1-mW signal is attenuated at the rate of 5 dB/1,000ft. What is the power level into a receiver that is 6,000 feet from the signal source?

answer: -30 dBm

4 . A power amplifier has a gain of 20 dB and an input level of 2 volts. Assuming that the input and output impedances are the same, what is the voltage level at the amplifier output? dB = 20 * log(voltage ratio)

answer: 20 V

5. A precision current shunt is measuring 100 millivolts across it. This indicates a current of 25 A. What is the actual resistance of this shunt?

answer: 0.004 Ω

6. A power system is providing 200 VAC at 25 A. The phase angle between current and voltage is 25°. What is the true power used by the system?

answer: 4531 W

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