An unknown length of copper wire and a 1.00-meter-long silver wire have the same cross-sectional area and resistance at 20°C. Calculate the length of the copper wire.

Respuesta :

Answer:

The length of the copper wire is 0.946 m.

Explanation:

Resistance ;

  • Resistance of a wire is directly proportional to its length.
  • Resistance of a wire is inversely proportional to the magnitude of its cross section area.

[tex]R\propto \frac{l}{A}[/tex]

[tex]\therefore R=\frac{\rho l}{A}[/tex]

[tex]\rho[/tex] is the resistivity of the wire, [tex]l[/tex] is the length of the wire and A is the cross section area of the wire.

The magnitude of resistivity of copper wire is 1.68×10⁻⁸Ωm.

The magnitude of resistivity of silver wire is 1.59×10⁻⁸Ωm.

The length of silver wire is 1.00 m

The resistance of the copper wire is

[tex]R_{Cu}=\frac{(1.68\times 10^{-8}\Omega m)\times l_{Cu} \ m}{A_{Cu}}[/tex]

The resistance of the silver wire is

[tex]R_{Ag}=\frac{(1.59\times 10^{-8}\Omega m)\times 1.00 \ m}{A_{Ag}}[/tex]

Given that,

[tex]R_{Cu}=R_{Ag}[/tex], [tex]A_{Cu}=A_{Ag}[/tex]

[tex]\therefore \frac{(1.68\times 10^{-8}\Omega m)\times l_{Cu}\ m}{A_{Cu}}=\frac{(1.59\times 10^{-8}\Omega m)\times1.00\ m}{A_{Ag}}[/tex]

[tex]\Rightarrow {(1.68\times 10^{-8}\Omega m)\times l_{Cu}\ m}={(1.59\times 10^{-8}\Omega m)\times 1.00 \ m}[/tex]  [[tex]A_{Cu}=A_{Ag}[/tex]]

[tex]\Rightarrow l_{Cu}=\frac{(1.59\times 10^{-8}\Omega m)\times 1.00 \ m} {(1.68\times 10^{-8}\Omega m)}[/tex]

[tex]\Rightarrow l_{Cu}=0.946[/tex] m

The length of the copper wire is 0.946 m.

The length of the copper wire will be "0.946 m".

Resistance

According to the question,

Resistivity of copper wire's magnitude = 1.68 × 10⁻⁸ Ωm

Resistivity of silver wire's magnitude = 1.59 × 10⁻⁸ Ωm

Silver wire's length = 1.00 m

We know that,

[tex]R_{Cu} = R_{Ag}[/tex],

[tex]A_{Cu} = A_{Ag}[/tex]

As we know the relation,

→ R ∝ [tex]\frac{l}{A}[/tex]

∴ R = [tex]\frac{\rho l}{A}[/tex]

here, ρ = Resistivity,

          l = length, and

         A = Cross section area

Now,

The copper wire's resistance will be:

R = [tex]\frac{1.68\times 10^{-8}\times l_{Cu}}{A_{Cu}}[/tex]

The silver wire's resistance will be:

R = [tex]\frac{1.59\times 10^{-8}\times 1.00}{A_{Ag}}[/tex]

According to the given information,

→ [tex]\frac{1.68\times 10^{-8}\times l_{Cu}}{A_{Cu}} = \frac{1.59\times 10^{-8}\times 1.00}{A_{Ag}}[/tex]

By applying cross-multiplication, we get

1.68 × 10⁻⁸ × [tex]l_{Cu}[/tex] = 1.59 × 10⁻⁸ × 1.00

                     [tex]l_{Cu}[/tex] = [tex]\frac{1.59\times 10^{-8}\times 1.00}{1.68\times 10^{-8}}[/tex]

                           = 0.946 m      

Thus the above response is correct.

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