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Question
A constantan wire has a length of 100 cm and a resistance of 12 Ω. If the specific resistance of constantan is 5 × 10−3 ohm cm. Calculate the area of cross-section of wire.
Numerical
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Solution
Given: l = 100 cm, R = 12 Ω, ρ = 5 × 10−3 Ω cm
Formula: \[R = \frac{\rho l}{A}\]
\[ A = \frac{\rho l}{R}\]
\[= \frac{(5 \times 10^{-3}\ \Omega \text{cm})(100\ \text{cm})}{12\ \Omega}\]
\[= \frac{0.5\ \Omega \text{cm}^2}{12\ \Omega}\]
= 0.041666 cm2
= 4.17 × 10−2 cm2
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Chapter 7: Electric Circuits, Resistance and Ohm's Law - EXERCISE-1 [Page 150]
