# Matrix Algebra.

• Jun 2nd 2011, 02:44 PM
ckeller
Matrix Algebra.
Hey everyone,

Could someone please shine some light on this question, I'm not sure I fully understand how it's worded?

Chris.

A range of metallic alloys are tested for electrical conductivity and give the following results for identically sized samples.

25% copper with 75% tin gave a reading of 0.0071 Ohms
40% copper with 40% tin and 20% cadmium gave a reading of 0.0060 Ohms

Using matrix algebra, determine the resistance of an equally sized sample for each of the pure metals –

(a) Copper
(b) Tin
• Jun 2nd 2011, 03:30 PM
skeeter
Quote:

Originally Posted by ckeller
Hey everyone,

Could someone please shine some light on this question, I'm not sure I fully understand how it's worded?

Chris.

A range of metallic alloys are tested for electrical conductivity and give the following results for identically sized samples.

25% copper with 75% tin gave a reading of 0.0071 Ohms
40% copper with 40% tin and 20% cadmium gave a reading of 0.0060 Ohms

Using matrix algebra, determine the resistance of an equally sized sample for each of the pure metals –

(a) Copper
(b) Tin

let [A] be a 3x3 matrix with percentages of copper, tin, and cadmium for each alloy

let [B] be a 3x1 matrix of the unknown resistances of each individual metal

let [C] be a 3x1 matrix of the measured resistance of each alloy

[A][B] = [C]

solve for matrix [B]

My calculator sez the resistances for copper, tin, and cadmium to be .0056, .0076, and .0036 ohms respectively.
• Jun 3rd 2011, 03:12 AM
ckeller
Quote:

Originally Posted by skeeter
let [A] be a 3x3 matrix with percentages of copper, tin, and cadmium for each alloy

let [B] be a 3x1 matrix of the unknown resistances of each individual metal

let [C] be a 3x1 matrix of the measured resistance of each alloy

[A][B] = [C]

solve for matrix [B]

My calculator sez the resistances for copper, tin, and cadmium to be .0056, .0076, and .0036 ohms respectively.

Hey Thanks very much for your reply it makes sense now.. although I have derived the same but smaller... 0.000056, 0.000076, and 0.000036...

I wonder where I went wrong there
• Jun 3rd 2011, 04:52 AM
skeeter
Quote:

Originally Posted by ckeller
Hey Thanks very much for your reply it makes sense now.. although I have derived the same but smaller... 0.000056, 0.000076, and 0.000036...

I wonder where I went wrong there

I suspect you failed to represent the given percentages as their decimal equivalents.
• Jun 3rd 2011, 05:44 AM
ckeller
Quote:

Originally Posted by skeeter
I suspect you failed to represent the given percentages as their decimal equivalents.

Hey yeah I realized that just as I posted my last comment, silly me lol