Question

A wire has a resistance of 20 Ω. Calculate the resistance of the wire when (3)
(i) only the length of the wire is doubled.
(ii) only the area of cross-section is doubled.
(iii) it is stretched to twice its original length.

Answer 1

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Answer 2

Answer: The resulting value of wire is 20.808 ohm.

Explanation:Given that,

Resistance R = 20 ohm

Increases length l = 2 %

The resistance is the product of the resistivity of the wire and length of the wire divided by the Area of the wire.

Volume of the wire . it remains constant.

Therefore, the resistance is directly proportional to the square of the length of the wire.

......(I)

The new length of the wire is

So, the new resistance of the wire is directly proportional to the square of the new length of the wire

.....(II)

Now, divided equation (I) by the equation (II)

Hence, The resulting value of wire is 20.808 ohm.

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