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A copper wire of uniform area of cross-section 3.4×10−5 m23.4×10^{-5}\space\text m^23.4×10−5 m2​ carries a current of 4.0 A. The magnit
Question

A copper wire of uniform area of cross-section 3.4×105 m23.4×10^{-5}\space\text m^2​ carries a current of 4.0 A. The magnitude of the electric field applied is ____________ (Resistivity of copper: 1.7×1081.7×10^{-8}​ Ω m).

A.

2.0×103 Vm2.0×10^{-3}\space\frac{\text V}{\text m}​​

B.

1.0×103 Vm1.0×10^{-3}\space\frac{\text V}{\text m}​​

C.

3.4×102 Vm3.4×10^{-2}\space\frac{\text V}{\text m}​​

D.

1.6×102 Vm1.6×10^{-2}\space\frac{\text V}{\text m}​​

Correct option is A

Given:Area of cross-section, A=3.4×105 m2Current, I=4.0 AResistivity of copper, ρ=1.7×108 Ωm\textbf{Given:} \\\begin{aligned}&\text{Area of cross-section, } A = 3.4 \times 10^{-5} \, \text{m}^2 \\&\text{Current, } I = 4.0 \, \text{A} \\&\text{Resistivity of copper, } \rho = 1.7 \times 10^{-8} \, \Omega \cdot \text{m}\end{aligned}

Let the length of the copper wire, L=1 m\text{Let the length of the copper wire, } L = 1 \, \text{m}

V=IR=IρLAV=41.7×10813.4×105V=41.7×1083.4×105=2.0×103 VV = IR = I \cdot \rho \cdot \frac{L}{A} \\[8pt]V = 4 \cdot 1.7 \times 10^{-8} \cdot \frac{1}{3.4 \times 10^{-5}} \\[8pt]V = \frac{4 \cdot 1.7 \times 10^{-8}}{3.4 \times 10^{-5}} = 2.0 \times 10^{-3} \, \text{V}

E=VL=2.0×1031=2.0×103 V/mE = \frac{V}{L} = \frac{2.0 \times 10^{-3}}{1} = 2.0 \times 10^{-3} \, \text{V/m}​​​​​

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