13. A very long straight, cylindrical wire lying along the x axis has a diameter of 0.250 mm and is initially at 20.0°C. It is made of a material described by Ohm's law with a resistivity of po = 3.30 x 10-8 Q. m and a temperature coefficient of resistivity of a = 0.00025 °C-1. Using a voltmeter, we measure a voltage of 8.00 V at a point that is 0.750 m to the right of a point that is measured to have zero voltage (see figure below). - Ax = 0.750 m- V = 0 V = 8.00 V a) What is the resistance per unit length of the wire? b) What are the magnitude and direction of the electric field in the section of the wire between the dashed lines? c) What are the magnitude and direction of the current in the wire between the dashed lines? d) What is the rate at which energy is dissipated in the section of the wire between the dashed lines? e) Now assume that the current found in part (c) flows through the entire wire. What is the magnitude and direction of the magnetic field generated by the wire at a distance of 1.00 m above the wire? f) The wire is now heated to 40.0 °C? Ignoring any changes to the size of the wire, what is the magnitude of the current in the wire?

13. A very long straight, cylindrical wire lying along the x axis has a diameter of 0.250 mm and is initially at 20.0°C. It is made of a material described by Ohm's law with a resistivity of po = 3.30 x 10-8 Q. m and a temperature coefficient of resistivity of a = 0.00025 °C-1. Using a voltmeter, we measure a voltage of 8.00 V at a point that is 0.750 m to the right of a point that is measured to have zero voltage (see figure below). - Ax = 0.750 m- V = 0 V = 8.00 V a) What is the resistance per unit length of the wire? b) What are the magnitude and direction of the electric field in the section of the wire between the dashed lines? c) What are the magnitude and direction of the current in the wire between the dashed lines? d) What is the rate at which energy is dissipated in the section of the wire between the dashed lines? e) Now assume that the current found in part (c) flows through the entire wire. What is the magnitude and direction of the magnetic field generated by the wire at a distance of 1.00 m above the wire? f) The wire is now heated to 40.0 °C? Ignoring any changes to the size of the wire, what is the magnitude of the current in the wire?