Announcements

1. Announcements Common Exam 3 is on MONDAY Nov 21st Exam will cover Multi-loop Kirchhoff circuits and RC circuits, Charges and Currents in Magnetic Fields, and Sources of Magnetic Fields (Biot-Savart, Amperes Law). Faraday’s Law of Induction (last weeks’s material) and AC circuits (this week’s material) will NOT be on Common Exam III. B A Option Review for the Common exam at 2:30pm today at 2:30pm. Location in Tiernan Lecture Hall 2 C

2. Inductors come is various shapes and sizes

3. Example – Metal Detector Hidden metal changes the flux of magnetic fields into a solenoid (inductor). The change in flux (and induced EMF) is detected and converted to an audio signal which the operator senses. Have you ever seen these “treasure hunters” on the New Jersey beaches?

4. Clicker Question #1 A coil of wire with zero resistance has its ends labeled A and B. The electric potential at A is higher than that at B. Which of the following could be consistent with this situation. The current is constant and is directed from A to B The current is constant and is directed from B to A The current is decreasing and is directed from A to B The current is increasing and is directed from B to A The current is decreasing and is directed from B to A A B C

5. Clicker Question #2 After closing the switch and waiting a LONG time, which of the following statements is true? A) The current in the resistor is constant and there is no measureable voltage across the inductor. B) The current in the inductor is constant and there is no measureable voltage across the resistor. C) The current in the resistor is zero and all of The voltage appears across in the inductor D) The voltage across the inductor is a Maximum and there is no voltage across the resistor E) All the above are false. B A C

6. Clicker Question #3 The RL circuit is initially charge by connecting the R and L in series with the battery. Then, the switch is moved (VERY quickly) to remove the battery from the circuit, thus connecting the R and L together. Which of the following statements are FALSE. A) Right when the switch is closed, current will flow continues to flow in the clockwise direction. B) If one waits long enough, the current in the resistor will approach zero. C) If one waits long enough, the current in the Inductor will approach zero. D) If one waits long enough, all of the energy In the inductor’s magnetic field is converted to Heat. E) When the switch is closed, the Current suddenly stops and then Begins to increase. B A C

7. Clicker Question #4 Which of the following things do not use magnetic induction in their operation: A) Inductive Reasoning B) Wireless Battery Chargers C) Cooking Stoves D) Flow meters E) Joysticks B A C

8. Dell Adds Wireless Battery Charging to New Laptop By Agam Shah, IDG News Dell introduced the Latitude Z business laptop, which includes a new wireless charging technology that could eventually find its way into other Dell systems, the company said on Tuesday. The Latitude Z can be placed on a special stand that generates an electromagnetic field to recharge laptop batteries wirelessly. The technology, which Dell calls inductive charging, takes the same amount of time to recharge laptop batteries as an AC adapter, said Steve Belt [CQ], vice president of business client engineering at Dell. "There's a coil in the bottom of the notebook and then there's a matching coil in the stand. You set them next to each other and it generates a current that flows and charges the battery," Belt said. B A MUTUAL INDUCTANCE C

9. Inductive Stoves Changing magnetic field in coil induces electric field (EMF) in the METAL cookware. The EMF drives current in the metal cookwear which heats the cookware from resistive losses.