Physics 9702 · AS & A Level · Resistance and resistivity

Resistance and resistivity — practice question

A heating-element wire has resistance $R$. It snaps and a different wire is fitted in its place. The table gives data for the original wire and the replacement wire. Original wire: length $l$, diameter $d$, resistivity of metal $\rho$. Replacement wire: length $l$, diameter $2d$, resistivity of metal $2\rho$. What is the resistance of the replacement wire?

  • A$\frac{R}{4}$
  • B$\frac{R}{2}$
  • C$R$
  • D$2R$

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