Question

During a laboratory experiment, a student finds
that at 20° Celsius, a 6.0-meter length of copper
wire has a resistance of 1.3 ohms. The crosssectional
area of this wire is
(1) 7.9 × 10^−8 m2 (3) 4.6 × 10^0 m2
(2) 1.1 × 10^−7 m2 (4) 1.3 × 10^7 m2

Answer 1

ρ = resistivity of copper at 20 °C = 1.72 x 10⁻⁸ ohm-m

R = resistance of the copper wire = 1.3 ohm

L = length of the copper wire = 6 meter

A = area of cross-section of the copper wire = ?

Resistivity of copper wire is given as

R = ρL/A

inserting the values in the above equation

1.3 = (1.72 x 10⁻⁸) (6)/A

A = 7.9 x 10⁻⁸ m²

Hence the correct choice is

(1) 7.9 x 10⁻⁸ m²

Answer 2

The cross-sectional area of the copper wire is which has 1.3 ohm at 20 degree Celsius during laboratory experiment by student is 7.9×10⁻⁸ ohm.

What is the resistance?

Resistance is obstacle for the current flow in the circuit. It is the measure of reverse act to current flow in through a material. It can be given as,

$R=\rho\dfrac{L}{A}$

Here, (ρ) is the specific resistance (l) is the length of the wire and (A) is the cross-sectional area of the wire.

During a laboratory experiment, the student finds that at 20° Celsius, a 6.0-meter length of copper wire has a resistance of 1.3 ohms.

The value of resistivity of copper wire is 1.72×10⁻⁸ ohm-m. Put these values in the above formula as,

$R=\rho\dfrac{L}{A}\\1.3=1.72\times10^{-8}\times\dfrac{6}{A}\\A=7.9\times10^{-8}\rm \; m^2$

Thus, the cross-sectional area of the copper wire is which has 1.3 ohm at 20 degree Celsius during laboratory experiment by student is 7.9×10⁻⁸ ohm.

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