There are three bulbs of 60W 100W and 200W which bulb has thickest filament ?
Correct answer: B. 200W
- A. 100W
- B. 200W
- C. 60W
- D. all
Explanation
At the same supply voltage, R = V²/P, so the 60 W bulb has the greatest resistance and therefore the smallest filament cross-sectional area. The 200 W bulb has the lowest resistance and needs the thickest filament. Option c, 60 W, is a likely mistake from confusing greater resistance with greater thickness.
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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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