Electricity: Electric Circuits
Electric Circuits: Audio Guided Solution
Problem 16:
A 3-way light bulb for a 110-V lamp has two different filaments and three different power ratings. Turning the switch of the lamp toggles the light from OFF to low (50 W) to medium (100 W) to high (150 W) brightness. These three brightness settings are achieved by channeling current through the high resistance filament (50 W), the low resistance filament (100 W) or through both filaments. Determine the resistance of the 50 W and the 100 W filaments.
Audio Guided Solution
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50-watt filament: R = 240 Ω (rounded from 242 Ω)
100-watt filament: R = 120 Ω (rounded from 121 Ω)
100-watt filament: R = 120 Ω (rounded from 121 Ω)
Habits of an Effective Problem Solver
- Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
- Identify the known and unknown quantities and record them in an organized manner. Equate given values to the symbols used to represent the corresponding quantity - e.g., ΔV = 9.0 V; R = 0.025 Ω; I = ???.
- Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
- Identify the appropriate formula(s) to use.
- Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.
Read About It!
Get more information on the topic of Electric Circuits at The Physics Classroom Tutorial.
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