Question

Given that the resistivity of Gold and Platinum is 2.1 × 10⁻⁸ and 10.5 × 10⁻⁸ ohm m, respectively, which is the correct statement?

STATEMENT A: 5 metres of platinum wire will have the same resistance as one metre of gold wire.

STATEMENT B: Gold wire of 1 cm radius will have the same resistance as platinum wire of 5 cm radius.

Options

• Only statement A is correct.

• Only statement B is correct.

• Both statements A and B are correct.

• Both statements A and B are incorrect.

Answer 1

Both statements A and B are incorrect.

Explanation:

Using \(R = \rho l/A\), platinum has 5 times the resistivity of gold. Statement A is false: with the same area, 5 m of platinum gives 25 times the resistance of 1 m of gold.

Statement B is false: for the same length, the platinum wire has 25 times the area but only 5 times the resistivity, so its resistance is one-fifth that of the gold wire.

Hence both statements are incorrect.