Exams › NEET › Physics

If a wire of resistance R is melted and recasted to half of its length, then the new resistance of the wire will be

1. R/4
2. R/2
3. R
4. 2R

Correct answer: R/4

Solution

Resistance of a wire is given by R = ρL/A, where L is the length and A is the cross-sectional area. When the wire is melted and recast to half its length, its volume remains constant, so the cross-sectional area doubles. Substituting L' = L/2 and A' = 2A into the formula, the new resistance becomes R' = ρ(L/2)/(2A) = R/4.

Related NEET Physics questions

• For a metallic wire, the ratio \( \frac{V}{i} \) (where, \( \mathbf{V}= \) applied potential difference and \( \mathbf{i}= \) current flowing
• In a metallic conductor, electric current is thought to be due to the movement of
• Assertion If the length of the conductor is doubled, the drift velocity will become half of the original value (keeping potential difference unchanged). Reason At constant potential difference, drift velocity is inversely proportional to the length of the conductor.
• The resistance of an iron wire is \( 10 \Omega \) and its temperature coefficient of resistance is \( 5 \times 10^{-3} /^{o} C . \) A current of \( 30 \mathrm{mA} \) is flowing in it at \( 20^{\circ} \mathrm{C} \). Keeping potential difference across its ends constant, if its temperature is increased to \( 120^{\circ} \mathrm{C} \) then the current flowing in the wire will be (in \( \mathrm{mA} \) )
• Wire of a certain material is stretched slowly be dep10. Its new resistance and specific resistance becomes respectively.
• Which of the following statements are wrong w.r.t the specific resistance of wire? This question has multiple correct options

⚔️ Practice NEET Physics free + battle 1v1 →