Which change decreases the resistance of a piece
of copper wire?
(1) increasing the wire’s length
(2) increasing the wire’s resistivity
(3) decreasing the wire’s temperature
(4) decreasing the wire’s diameter

Explanation :

We know that the resistance of the wire is given by :

Where

is the resistivity

l is the length of the wire

A is the area of the wire.

Another factor on which the resistance of wire depends is temperature. It is given by :

So, it is clear that the resistance of the wire is directly proportional to the temperature. It we want to decrease the resistance of the piece, its temperature should be decreased.

So, the correct option is (3) " decreasing the wire’s temperature ".

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c) both a and b.

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