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Chapter 17 Section 3 Current and Resistance Objectives • Recognize what causes charges to flow through a circuit/conductor • Describe the basic properties of electric current, and solve problems relating current, charge, and time. • Distinguish between the drift speed of a charge carrier and the average speed of the charge carrier between collisions. © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance What are the requirements for a charge to move through a conductor? What charges are the ones that flow through the conductor? © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Electronic Current and Conventional Current: Electronic Current • Is described as the flow of electrons. • Electrons flow from the negative terminal to the positive. Conventional Current • Conventional current or simply current, behaves as if positive charge carriers cause current flow. • Conventional current flows from the positive terminal to the negative. A charge Carrier is a particle that carries an electric charge © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Electronic Current and Conventional Current: © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Current and Charge Movement • If 7200 cars pass a toll gate “SALIK” in 1 hour, what is the rate of flow of cars through that gate each second. © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Current and Charge Movement • Now, if Electric current is defined as the rate at which electric charges pass through a given area, write a formula to calculate the electric current. © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Current and Charge Movement • Electric current is the rate at which electric charges pass through a given area. I electric current = Q t charge passing through a given area time interval © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance What do you think??! How does the current change if the number of charge carriers increases? How does the current change if the time interval during which a given number of charge carriers pass the cross-sectional area increases? © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Sample Problem C Page 597: The current in a light bulb is 0.835 A. How long does it take for a total charge of 1.67 C to pass through the filament of the bulb? © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Practice Problems Page 597: © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Extra Practice: © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Extra Practice: Describe the relationship between electric potential difference and electric current © Houghton Mifflin Harcourt Publishing Company Chapter 17 Section 3 Current and Resistance Drift Velocity • Drift velocity is the net velocity of a charge carrier moving in an electric field. • When an electron moves through a conductor, collisions with the vibrating metal atoms of the conductor force the electron to change its direction constantly. Change in direction Velocity change. © Houghton Mifflin Harcourt Publishing Company Drift speeds are relatively small because of the many collisions that occur when an electron moves through a conductor. Chapter 17 Section 3 Current and Resistance What Causes Charges to Flow through a Conductor? What opposes the flow of charges through a conductor? © Houghton Mifflin Harcourt Publishing Company