A copper telephone wire has essentially no sag between poles 36.0 m apart on a winter day when the temperature is −20.0°C. How much longer is the wire on a summer day when the temperature is 34.0°C?

The extension is  

Explanation:

From the question we are told that  

     The length of the wire on a winter day is    

      The temperature on the winter day is  

      The temperature on a summer day is  

The the extension of the wire on a summer day is mathematically represented as

Where  

      is the  coefficient of linear expansion of copper with a values

substituting value  

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.