Physics, 06.11.2019 22:31 tinyturtles

The resistivity of gold is 2.44 x 10-8 ohms. m at room temperature. a gold wire that is 0.9 mm in diameter and 14 cm long carries a current of 940 ma. what is the electric field in the wire?
answer

0.090 v/m

0.028 v/m

0.046 v/m

0.0090 v/m

0.036 v/m

Answers: 2

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Answer from: justinc10

The electric field in the gold wire is 0.036V/m.

Hence, Option E) 0.036V/m is the correct answer.

Given the data in the question;

The resistivity of gold; $p = 2.44 * 10^{-8} ohms.m$ Diameter of gold wire; d = 0.9mm = 0.0009m

Length of the gold wire; l = 14cm = 0.14m

Current;

Electric field in the wire; $E =\ ?$

First we find the cross-sectional area of the gold wire;

Area; $A = \pi r^2 = \pi (\frac{d}{2})^2$

We substitute in our values

$A = \pi (\frac{0.0009m}{2})^2 \\\\A = 6.36*10^{-7}m^2$

Next, we calculate the current density( J ), which is the ratio of Current to Area

Current density( J ) = Current / Area

$J = \frac{I}{A}$

We substitute our values into the equation

$J = \frac{0.94A}{6.36*10^{-7}m^2} \\\\J = 1.478 * 10^6 A/m^2$

Now, We know that, using the expression for electric field (E) inside a current conductor:

E = pJ

Where E is electric field, is the resistivity of gold and the current density.

We substitute our values into the equation

$E = (2.44 * 10^{-8} ohms.m) * ( 1.478*10^6A/m^2)\\\\E = 0.036 V/m$

The electric field in the gold wire is 0.036V/m.

Hence, Option E) 0.036V/m is the correct answer.

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Answer from: bluexorsit7603

E=0.036 V/m

Explanation:

Given that

Resistivity ,ρ=2.44 x 10⁻⁸ ohms.m

d= 0.9 mm

L= 14 cm

I = 940 m A = 0.94 A

We know that electric field E

E= V/L

V= I R

R=ρL/A

So we can say that

E= ρI/A

Now by putting the values

$E=\dfrac{ 2.44\times 10^{-8}\times 0.94}{\dfrac{\pi}{4}(0.9\times 10^{-3})^2}$

E=0.036 V/m

Answer from: Quest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

Answer from: Quest

Are there options for this?

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The resistivity of gold is 2.44 x 10-8 ohms. m at room temperature. a gold wire that is 0.9 mm in di...

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