Question 707: Current Electricity

Question

The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then

Accepted Answer

Resistance of wire  = $$\rho {l \over A}$$
$$R \propto {l \over A} = {l \over {\pi {r^2}}}$$
When length and radius are both doubled
$${R_1} \propto {{2l} \over {\pi {{\left( {2r} \right)}^2}}} \Rightarrow {R_1} \propto {1 \over 2}R$$
The specific resistance of wire is independent of geometry of the wire, it only depends on the material of the wire.

Answer

The resistance will be doubled and the specific resistance will be halved.

Answer

The resistance will be halved and the specific resistance will remain unchanged.

Answer

The resistance will be halved and the specific resistance will be doubled.

Answer

The resistance and the specific resistance, will both remain unchanged.

Current Electricity

The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then

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