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Science · 2025 · 3 marks
CBSE 2025 · Region 1 · Set 1 · Q33
(a) Write the relationship between resistivity and resistance of a cylindrical conductor of length l and area of cross-section A. Hence derive the SI…
(a)
Write the relationship between resistivity and resistance of a cylindrical conductor of length $\displaystyle l$ and area of cross-section A. Hence derive the SI unit of resistivity.
(b)
Why are alloys used in electrical heating devices ?
Marking-scheme solution
(a)
\(\displaystyle \mathrm{R}=\rho \frac{l}{A}\)
\(\displaystyle \rho=\frac{R A}{l}\)
SI unit of \(\displaystyle \rho=\frac{\text { ohm } \text { × }(\text { metre })^{2}}{\text { metre }}\)
= ohm meter
(b)
Resistivity of alloy is higher than pure metals. / They do not oxidise (burn) readily at high temperatures.
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.