A filament lamp is marked and is designed for a sinusoidal supply of root-mean-square at

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electromagnetic induction and alternating-current circuits · Electromagnetic induction and alternating-current circuits

Electricity, Magnetism and Electromagnetism, Ch Alternating current: peak and rms values, the oscilloscope and rectification

Problem

A filament lamp is marked

96\,\mathrm{W}

and is designed for a sinusoidal supply of

120\,\mathrm{V}

root-mean-square at

60\,\mathrm{Hz}

. Treat the lamp as a pure resistance whose value does not change over the cycle, and take the marked power as the mean power. ((a)) Find the root-mean-square current in the lamp. ((b)) Find the peak instantaneous power dissipated in the lamp. ((c)) An ideal oscilloscope, drawing no current, is connected across the lamp with the vertical sensitivity set to

50\,\mathrm{V}

per division. How many divisions above the zero line does the crest of the trace lie? ((d)) With the time base set to

2.0\,\mathrm{ms}

per division, how many horizontal divisions does one complete cycle occupy?

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