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NEET 1988 (AIPMT) · Ohm's Law, Resistivity & Temperature

Ohm's Law, Resistivity & Temperature question from NEET 1988 (AIPMT)

Q80NEET 1988 · AIPMTMedium

Ohm's Law, Resistivity & Temperature

The masses of the wires of copper is in the ratio of 1:3:51 : 3 : 5 and their lengths are in the ratio of 5:3:15 : 3 : 1. The ratio of their electrical resistance is

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Answer: (d)

  1. Mass m=dlA⇒A=m/(dl)m = dlA \Rightarrow A = m/(dl), so R=ρl/A=ρd l2/m∝l2/mR = \rho l/A = \rho d\,l^2/m \propto l^2/m.
  2. R1:R2:R3=251:93:15=25:3:0.2R_1 : R_2 : R_3 = \dfrac{25}{1} : \dfrac{9}{3} : \dfrac{1}{5} = 25 : 3 : 0.2
  3. Multiply by 5: 125:15:1125 : 15 : 1. The answer is (d).
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