What Metal Is the Wire Made Of Based on Its Resistivity?

[goWlfpack]

Homework Statement

A wire, 50.0 m long and 2.00 mm in diameter is connected to a source with a potential difference of 9.11 V, and the current is found to be 23.45 A. Assume a temperature of 20°C and using Table 17.1, identify the metal out of which the wire is made of.

Homework Equations

R=p(l/A)

where R is the resistance p is the coefficient of resistivity, l is the length and A is the area

The Attempt at a Solution

ok since we are solving for p first i found R by the equation V=IR and found R to be .388
next i found the area using the surface area of a cylinder and found that to be .628
next i divided length by .628 and found that to be 79.618
so then i divided .388/79.618 and got 4.8*10^-3
thats the right magnitude but it does match any of my options coefficients.

the problem let's me choose whether the metal is gold, silver, copper, or iron.

 

[olgranpappy]

Homework Statement

A wire, 50.0 m long and 2.00 mm in diameter is connected to a source with a potential difference of 9.11 V, and the current is found to be 23.45 A. Assume a temperature of 20°C and using Table 17.1, identify the metal out of which the wire is made of.

Homework Equations

R=p(l/A)

where R is the resistance p is the coefficient of resistivity, l is the length and A is the area

The Attempt at a Solution

ok since we are solving for p first i found R by the equation V=IR and found R to be .388
next i found the area using the surface area of a cylinder and found that to be .628

wrong area. you want the cross-sectional area of the wire

next i divided length by .628 and found that to be 79.618
so then i divided .388/79.618 and got 4.8*10^-3
thats the right magnitude but it does match any of my options coefficients.

the problem let's me choose whether the metal is gold, silver, copper, or iron.

 

[goWlfpack]

ugh ok i got the area by .002*.002*3.14 = .00001256
then i divided 50/.00001256 and got 3980891.72
so then i divided my R .388 by 3980891.72 an got 9.74e-8
not right...

 

[goWlfpack]

please help i really don't understand why this is still wrong...

 

[olgranpappy]

you still have the wrong number for the area. The *diameter* is 0.002. The *radius* is 0.001.
You used Area=diameter*diameter*Pi, which is wrong.

Area=radius*radius*Pi