Which one of the following bulbs has the least resistance ?
Correct answer: C. 300 watt
- A. 100 watt
- B. 200 watt
- C. 300 watt
- D. 60 watt
Explanation
For bulbs designed for the same voltage, R = V²/P, so resistance is inversely proportional to rated power. Thus the 300 W bulb has the least resistance: R = V²/(300 W), whereas the 100 W option has a larger resistance and is the most likely distractor.
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About Resistance and Resistivity
Resistance measures opposition to current in a conductor and follows R = V/I for an ohmic conductor, while resistivity is an intrinsic property of the material. Questions use R = ρL/A, examine effects of length, cross-sectional area and temperature, and distinguish resistance, resistivity, conductance and conductivity.
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