7. A 100 W incandescent lamp has a resistance when cold (lamp extinguished) that is only 1/12 of its hot (lamp illuminated) resistance value. a) What is the lamp current and its hot resistance when placed across a 120 V line? b) What is the cold resistance of this lamp? c) What is the instantaneous current through the lamp at the moment it is switched on? d) What power does the lamp dissipate at this instant?

Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List)
10th Edition
ISBN:9781337399128
Author:Russell E. Smith
Publisher:Russell E. Smith
Chapter13: Heating Control Devices
Section: Chapter Questions
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7. A 100 W incandescent lamp has a resistance when cold (lamp extinguished) that
is only 1/12 of its hot (lamp illuminated) resistance value.
a) What is the lamp current and its hot resistance when placed across a 120 V
line?
b) What is the cold resistance of this lamp?
c) What is the instantaneous current through the lamp at the moment it is
switched on?
d) What power does the lamp dissipate at this instant?
Transcribed Image Text:7. A 100 W incandescent lamp has a resistance when cold (lamp extinguished) that is only 1/12 of its hot (lamp illuminated) resistance value. a) What is the lamp current and its hot resistance when placed across a 120 V line? b) What is the cold resistance of this lamp? c) What is the instantaneous current through the lamp at the moment it is switched on? d) What power does the lamp dissipate at this instant?
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