Question

The resistance of copper wire is 3 ohms at 25€ Find the resistance of the same wire at 200C
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Answer 1

Explanation:

Given : RT=60 ohms @ T=500oC

Also, RT′=20 ohms @ T′=20oC

Resistance at a given temperature RT=RT′[1+α(T−T′)]

∴ 60=20[1+α(500−20)]

⟹ α=4802=0.00417

Let resistance of wire is 25 ohm at temperature T′′.

∴ RT′′=RT′[1+α(T′′−T′)]

OR  25=20[1+(0.00417)(T′′−20)]

⟹ T′′=80oC