Calculating the Total Resistance of a Composite Wire

[ninanoorable]

Homework Statement

A 10.0 length of wire consists of 5.0 of copper followed by 5.0 of aluminum, both of diameter 1.3 . A voltage difference of 87 is placed across the composite wire.What is the total resistance (sum) of the two wires?

Homework Equations

R=pL/A

The Attempt at a Solution

R1=1.72*10-8 *5/3.14*(0.65*10-3)2 and I've done the same method for R2 and added them to get R total..but it was wrong..i thought this question is simple..but idon't know why i couldn't solve it..help please..thanks

 

[eczeno]

Homework Statement

A 10.0 length of wire consists of 5.0 of copper followed by 5.0 of aluminum, both of diameter 1.3 . A voltage difference of 87 is placed across the composite wire.What is the total resistance (sum) of the two wires?

Homework Equations

R=pL/A

The Attempt at a Solution

R1=1.72*10-8 *5/3.14*(0.65*10-3)2 and I've done the same method for R2 and added them to get R total..but it was wrong..i thought this question is simple..but idon't know why i couldn't solve it..help please..thanks

hello,

it seems your idea is right. it would help if you supplied units for the given quantities.

there may be some problems with order of operations when you plug the numbers in. here is how you should type it into your calculator (you don't need all the spaces, i just put them into make it easier to read):

1.72 * 10^-8 * 5 / ( 3.14 * (0.65 * 10^-3)^2 )

 

[ninanoorable]

thank you..but it didn't work either..i just donno what's wrong

 

[ninanoorable]

mmm.i've just found what was wrong after using all my attempts...it's silly ..the site wanted the answer in 2 significant figures...

 

[eczeno]

oh dear, that can be frustrating. one must try to find the humor in these things else one might punch a hole in one's computer screen.