A new material is found to be superconducting below 77 K. How much resistance will a 75 mm long sample of this material have if it is at a temperature of 69.3 K while connected to a 6.4 V AC-power supply? R =       How much thermal energy will it generate? Thermal energy generated =

Consider a power plant is located 60 km away from a residential area uses Q-gauge (A=42.40mm2) wire ofcopper to transmit power at a current of I = 100.00 A.How much more power is dissipated in the copper wires than it would be in superconducting wires?

A close analogy exists between the flow of energy by heat because of a temperature difference (see Section 19.6) and the flow of electric charge because of a potential difference. In a metal, energy dQ and electrical charge dq are both transported by free electrons. Consequently, a good electrical conductor is usually a good thermal conductor as well. Consider a thin conducting slab of thickness dx, area A, and electrical conductivity , with a potential difference dV between opposite faces. (a) Show that the current I = dq/dt is given by the equation on the left: ChargeconductionThermalconductiondqdt=A|dVdx|dQdt=kA|dTdx| In the analogous thermal conduction equation on the right (Eq. 19.17), the rate dQ/dt of energy flow by heat (in SI units of joules per second) is due to a temperature gradient dT/dx in a material of thermal conductivity k. (b) State analogous rules relating the direction of the electric current to the change in potential and relating the direction of energy flow to the change in temperature.

A 20.00-V battery is used to supply current to a 10-k resistor. Assume the voltage drop across any wires used for connections is negligible, (a) What is the current through the resistor? (b) What is the power dissipated by the resistor? (c) What is the power input from the battery; assuming all the electrical power is dissipated by the resistor? (d) What happens to the energy dissipated by the resistor?