Homework help- electrical resistance

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SUMMARY

The discussion centers on calculating the diameter of a tungsten filament in a lightbulb, given its resistance of 0.041 ohms, a length of 2.5 cm (0.025 m), and a resistivity of 5.6 × 10-8 ohm-meters. The formula used is R = ρ(L / (2πr²)), where R is resistance, ρ is resistivity, L is length, and r is the radius. The incorrect calculation of 20856 m indicates a misunderstanding of unit conversion or formula application, necessitating a review of the calculation process to derive the correct diameter in millimeters.

PREREQUISITES
  • Understanding of electrical resistance and its units (ohms)
  • Familiarity with the concept of resistivity in materials
  • Knowledge of geometric formulas, particularly for circles
  • Ability to perform unit conversions accurately
NEXT STEPS
  • Review the formula for calculating resistance in cylindrical conductors
  • Practice unit conversion techniques, especially for metric units
  • Explore the properties of tungsten and its applications in electrical components
  • Learn about the significance of resistivity in material science
USEFUL FOR

This discussion is beneficial for students studying physics or electrical engineering, particularly those focusing on circuit design and material properties. It also aids educators looking for practical examples of resistance calculations.

bob12345
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Homework Statement



A 2.5 cm length of tungsten filament in a
small lightbulb has a resistance of 0.041
.
Find its diameter. (The resistivity is
5.6 × 10−8
· m).
Answer in units of mm.

Homework Equations



R=P(L/2pi*rsquared)

The Attempt at a Solution


i keep getting 20856 m as my answer but it is wrng when i entr it i plugged in everything and made sure everything was to the right unit so don't know what is wrong
 
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Take care of units. The resistance of the filament is 0.041 ohm, the resistvity is 5.6 x10-8 ohm-meter, and the length is 0.025 m. How could you get such a result for the diameter of a tiny filament? Show your calculation.

ehild
 

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