A 160.0 km long electric power line made out of copper is installed during the Spring months at an average temperature of 10.2 °C.
1) What is the change in the length of the power line on a hot summer day, when the temperature is 32.1 °C? The coefficient of linear expansion for copper is 1.62×10^(-5) 1/C°. Use a positive sign for an increase in length and negative for a decrease.
2) What is the change in the length of the cable on a -28.7 °C cold Winter day?

1.+160.0567km

2.-0.102km

Explanation:

Given initial length L1=160Km

L2=?

Initial temperature=10.2°C

Final temperature=32.1°c

Coefficient of linear expansivity a= 1.62*10^-5per Celsius

1: a=L2-L1/L1*∆T

(L2-160/160*21.9)=1.62*10^-5

L2-160=0.0567

L2= 0.0567+160

L2=160.0567Km

2.∆L=? at -28.7°C

Also a=∆L/L1∆T

We're ∆L= aL1∆T

1.65*10^-5*160*(-28.7-10.2)

=-0.102km

- measure reactants precisely. ( first choice)

- stir to the reaction take place. ( second choice)

- wait patiently until the reaction completes. ( fourth choice)

- make sure to recover as much copper as possible. ( last choice)

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it