If length of the wire becomes two times to its orignal value and area becomes one half to its orignal value, than resistance of the wire becomes:
Correct answer: D. 4 times
- A. Double
- B. One Forth
- C. One half
- D. 4 times
Explanation
Resistance (R) is directly proportional to the length (L) and inversely proportional to the cross-sectional area (A) of the wire. If length doubles (2x) and area reduces to half (1/2x), the resistance becomes (2x) / (1/2x) = 4 times the original resistance
This question appeared on the NUMS 2023 paper, which you can sit online with every answer explained.
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About Resistance and Resistivity
Resistance measures opposition to current in a conductor and follows R = V/I for an ohmic conductor, while resistivity is an intrinsic property of the material. Questions use R = ρL/A, examine effects of length, cross-sectional area and temperature, and distinguish resistance, resistivity, conductance and conductivity.
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