QuestionsCh25 - CHAPTER 25: Electric Currents and...

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CHAPTER 25: Electric Currents and Resistance Responses to Questions A battery rating in ampere-hours gives the total amount of charge available in the battery. 2. The chemical reactions within the cell cause electrons to pile up on the negative electrode. If the terminals of the battery are connected in a circuit, then electrons flow from the negative terminal because it has an excess of electrons. Once the electrons return to the cell, the electrolyte again causes them to move to the negative terminal. 3. When a flashlight is operated, the battery energy is being used up. 4. The terminal of the car battery connected to “ground” is actually connected to the metal frame of the car. This provides a large “sink” or “source” for charge. The metal frame serves as the common ground for all electrical devices in the car, and all voltages are measured with respect to the car’s frame. 5. Generally, water is already in the faucet spout, but it will not come out until the faucet valve is opened. Opening the valve provides the pressure difference needed to force water out of the spout. The same thing is essentially true when you connect a wire to the terminals of a battery. Electrons already exist in the wires. The battery provides the potential that causes them to move, producing a current. 6. Yes. They might have the same resistance if the aluminum wire is thicker. If the lengths of the wires are the same, then the ratios of resistivity to cross-sectional area must also be the same for the resistances to be the same. Aluminum has a higher resistivity than copper, so if
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This note was uploaded on 03/22/2009 for the course PHY 54L taught by Professor Thomas during the Spring '09 term at Duke.

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QuestionsCh25 - CHAPTER 25: Electric Currents and...

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