The definition of resistivity implies that an electric field exists inside a conductor. yet we know that there can be no electric field inside a conductor. is there a contradiction here? explain.

There no electric field in a superconductor, since a superconductor has 0 resistance (and 0 resistivity).

Ordinary mere mortal conductors like silver and copper do have a little resistance and hence do have small electric fields inside. They are not perfect conductors.

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the answer is a. at the equator

double the distance = divide strength by 4