Resistance of a Wire – Rankers Physics
Topic: Current Electricity
Subtopic: Basics of Current

Resistance of a Wire

A certain wire \(A\) has resistance \(81 \Omega\). The resistance of another wire \(B\) of same material and equal length but of diameter thrice the diameter of \(A\) will be
\(729 \Omega\)
\(243 \Omega\)
\(81 \Omega\)
\(9 \Omega\)

Solution:

Resistance is inversely proportional to the square of the diameter: \(R = \frac{1}{d^2}\). Since the diameter is tripled, the resistance becomes \(\frac{R}{9} = \frac{81}{9} = 9 \Omega\).

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