PHYS 102 CHAPTER 7 HOMEWORK
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A current of 20.4 A flows through an electric heater operating on 120 V. What is the heater's resistance? A 340 立 resistor is connected to a variablevoltage power supply. A current of 11.0 A flows through an electric heater operating on 120 V. Compute the power consumption of the electric heater. An electric train operates on 890 V. What is its power consumption when the current flowing through the train's motor is 2,030 A? All of the electrical outlets in a room are connected in a single parallel circuit. The circuit is equipped with a 20 A fuse, and the voltage is V = 220 V Your cell phone typically consumes about 330 mW of power when you text a friend. If the phone is operated using a lithiumion battery with a voltage of 3.5 V, what is the current flowing through the cellphone circuitry under these circumstances? An electric clothes dryer is rated at 2,400 W. How much energy does it use in 20 min? A certain electric motor draws a current of 78 A when connected to 120 V. An electric car is being designed to have an average power output of 6,700 W for 2 h before needing to be recharged. (Assume there is no wasted energy.) A solid metal cylinder has a certain resistance. It is then heated and carefully stretched to form a longer, thinner cylinder. After it cools, will its resistance be the same as, greater than, or less than what it was before? If a new material is found that is a superconductor at all temperatures, what parts of some common electric devices would definitely not be made out of it? (Select all that apply.) A simple electric circuit consists of a constantvoltage power supply and a variable resistor. What effect does reducing the resistance have on the current in the circuit and on the power output of the power supply? What is the purpose of having fuses or circuit breakers in electric circuits? How should they be connected in circuits so they will be effective?
A 20A fuse in a household electric circuit burns out. What catastrophe could occur if it is replaced by a 30A fuse?