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ICSE Class 10 Physics Question 15 of 15

Solved 2022 Semester 2 Question Paper ICSE Class 10 Physics — Question 15

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Question

Question 6(iii)

If a wire of resistance 2Ω gets stretched to thrice its original length :

(a) Calculate the new resistance of the wire.

(b) What happens to the specific resistance of the wire?

Answer

(a) Given, R = 2Ω

⇒ ρlA\dfrac{\text{l}}{\text{A}} = 2Ω

Let new resistance be R'.

New length = 3l3\text{l}

New Area = A3\dfrac{\text{A}}{3}

∴ R' = ρ3lA3\dfrac{\text{3l}}{\dfrac{\text{A}}{3}}

= ρ9lA\dfrac{\text{9l}}{\text{A}}

= 9R = 9 × 2 = 18Ω

Hence, new resistance = 18Ω

(b) Specific resistance of the wire remains unchanged since it does not depend on the dimensions of the wire. It is the characteristic property of the substance.