27. Resistors & DC Circuits

Power in Circuits

27. Resistors & DC Circuits

# Power in Circuits - Video Tutorials & Practice Problems

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## Power in Circuits

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2

Problem

ProblemA hair dryer operates at 120 V (the voltage produced by a household outlet), and outputs 1200 W of energy. For this problem, treat the hair dryer as a single resistor.

(a) At what current does the hair dryer operate?

(b) What is the resistance of the hair dryer?

A

(a) i=0.1 A;

(b) R=8.3×10

(b) R=8.3×10

^{−5}ΩB

(a) i=10 A;

(b) R=0.083 Ω

(b) R=0.083 Ω

C

(a) i=10 A;

(b) R=12 Ω

(b) R=12 Ω

D

(a) i=0.1 A;

(b) R=120,000 Ω

(b) R=120,000 Ω

3

Problem

ProblemAn incandescent lightbulb produces 100 W of light. If this lightbulb operates at 25% efficiency (meaning that out of all the power it generates, only 25% is released as light), what resistance must the lightbulb have if it operates at 120 V?

A

36 Ω

B

144 Ω

C

576 Ω

D

5.76 × 10

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PRACTICE PROBLEMS AND ACTIVITIES (13)

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