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Current Electricity question

2023 · Q167
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Current Electricity question

2023 · Q167

NEETPhysicsCurrent ElectricityMCQ+4 / −1

The resistance of platinum wire at 0∘C0^{\circ} \mathrm{C}0∘C is 2 Ω2 ~\Omega2 Ω and 6.8 Ω6.8 ~\Omega6.8 Ω at 80∘C80^{\circ} \mathrm{C}80∘C. The temperature coefficient of resistance of the wire is :

  1. A
    3×10−3C−13 \times 10^{-3} \mathrm{C}^{-1}3×10−3C−1
  2. B
    3×10−2C−13 \times 10^{-2} \mathrm{C}^{-1}3×10−2C−1
  3. C
    3×10−10C−13 \times 10^{-10} \mathrm{C}^{-1}3×10−10C−1
  4. D
    3×10−4C−13 \times 10^{-4} \mathrm{C}^{-1}3×10−4C−1
View written solutionFree

Correct answer: B

$$\mathrm{R}_{\mathrm{T}}=\mathrm{R}_{0}\left[1+\alpha\left(\mathrm{T}-\mathrm{T}_{0}\right)\right]$$

$$6.8=2[1+\alpha(80-\alpha)]$$

$$\alpha=\frac{2.4}{80}=0.03 /{ }^{\circ} \mathrm{C}=3 \times 10^{-2} /{ }^{\circ} \mathrm{C}$$

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