The resistance of a wire of length 250 m is 1 ohm. If the resistivity of the material of wire is 1.6 x 10 – 8 ohm meter, find the area of cross - section of the wire. How much does the resistance change if the diameter is doubled?
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Resistance = 1 Ω
Length = 250 metre
Resistivity = 1.6*10⁻⁸
R = ρl / A
So,
1 = 1.6 * 10⁻⁸ * 250 / A
A = 1.6 * 10⁻⁸ * 1000/4
A = 0.4 * 10⁻⁸ * 10³
A = 4 * 10⁻⁶ m².
∴ Area of the cross section = 4 * 10⁻⁶
Length = 250 metre
Resistivity = 1.6*10⁻⁸
R = ρl / A
So,
1 = 1.6 * 10⁻⁸ * 250 / A
A = 1.6 * 10⁻⁸ * 1000/4
A = 0.4 * 10⁻⁸ * 10³
A = 4 * 10⁻⁶ m².
∴ Area of the cross section = 4 * 10⁻⁶
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