A copper wire of length 10 m and radius (10⁻³/√π) m has electrical resistance 10 Ω. The current density if an electric field strength of 10 V/m is applied is:
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A copper wire of length 10 m and radius (10⁻³/√π) m has electrical resistance 10 Ω. The current density if an electric field strength of 10 V/m is applied is:

G1 Physics · Accepted Answer

Step 1: Area A = πr² = 10⁻⁶ m². Step 2: Resistivity ρ = RA/l = (10 × 10⁻⁶)/10 = 10⁻⁶ Ω·m. Step 3: Current density J = E/ρ = 10/(10⁻⁶) = 10⁷ A/m².