Primary coil Secondary coil FIGURE VI.2 R
Your laptop has wireless communications connectivity, and you might even have a wireless keyboard or mouse. But there’s one wire you haven’t been able to get rid of yet—the power cord.
Researchers are working on ways to circumvent the need for a direct electrical connection for power, and they are experiencing some success. Recently, investigators were able to use current flowing through a primary coil to power a 60 W lightbulb connected to a secondary coil 2.0 m away, with approximately 15% efficiency. The coils were large and the efficiency low, but it’s a start. The wireless power transfer system is outlined in Figure VI.2. An AC supply generates a current through the primary coil, creating a varying magnetic field. This field induces a current in the secondary coil, which is connected to a resistance (the lightbulb) and a capacitor that sets the resonance frequency of the secondary circuit to match the frequency of the primary circuit.
What are the rms and peak currents for a 60 W bulb? (The rms voltage is the usual 120 V.)
A. 0.71 A, 0.71 A B. 0.71 A, 0.50 A
C. 0.50 A, 0.71 A D. 0.50 A, 0.50 A
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