31. Alternating Current

A person touches a wire carrying a 120 V AC voltage. One hand touches the wire, and both of the person's feet are bare and are touching the ground. Assume skin resistance at the hand and at each foot is $2200\Omega$. What is the current through the person's torso?

You have a special light bulb with a very delicate wire filament. The wire will break if the current in it ever exceeds 1.50 A, even for an instant. What is the largest root-mean-square current you can run through this bulb?

Off to Europe! You plan to take your hair dryer to Europe, where the electrical outlets put out 240 V instead of the 120 V seen in the United States. The dryer puts out 1600 W at 120 V. (a) What could you do to operate your dryer via the 240-V line in Europe?

Off to Europe! You plan to take your hair dryer to Europe, where the electrical outlets put out 240 V instead of the 120 V seen in the United States. The dryer puts out 1600 W at 120 V. (b) What current will your dryer draw from a European outlet? (c) What resistance will your dryer appear to have when operated at 240 V?

Commercial electricity is generated and transmitted as three-phase electricity. Instead of a single emf, three separate wires carry currents for the emfs ε₁=ε​₀ cos ωt, ε₂=ε₀ cos(ωt +120°), and ε₃=ε₀ cos(ωt−120°) over three parallel wires, each of which supplies one-third of the power. This is why the long-distance transmission lines you see in the countryside have three wires. Suppose the transmission lines into a city supply a total of 450 MW of electric power, a realistic value. a. What would be the rms current in each wire if the transmission voltage were ε​₀=120 V rms?

Commercial electricity is generated and transmitted as three-phase electricity. Instead of a single emf, three separate wires carry currents for the emfs ε₁=ε​₀ cos ωt, ε₂=ε₀ cos(ωt +120°), and ε₃=ε₀ cos(ωt−120°) over three parallel wires, each of which supplies one-third of the power. This is why the long-distance transmission lines you see in the countryside have three wires. Suppose the transmission lines into a city supply a total of 450 MW of electric power, a realistic value. b. In fact, transformers are used to step the transmission-line voltage up to 500 kV rms. What is the current in each wire?