Question

A platinum wire is used to determine the melting point of indium. The resistance of the platinum wire is 2.000 Ω at 20°C and increases to 3.072 Ω as indium starts to melt. What is the melting point of indium? (The temperature coefficient of resistivity for platinum is 3.9 ×

Answer 1

Answer:

The melting point of indium is 157.436 degrees Celsius.

Explanation:

The resistance of the platinum wire, R1 = 2

The temperature at R1 is, T1 = 20 degrees Celsius.

The increased resistance, R2 = 3.072

Let the temperature at 3.072 = T2

Now find the temperature at which the indium starts melting.

We know that α = ( R2 - R1 ) / [ R1 × ( T2 - T1 ) ]

Given, α = 3.9 x 10^-3/ degrees Celsius.

T2- T1   = ( R2 - R1 ) / R1 α

T2 – T1 = (3.072 – 2) / (2 × 3.9 x 10^-3)

T2 – T1 = 137.436

T2 = T1 + 137.436

T2 =  20 + 137.436

T2 = 157.436 degree Celsius