1. Copyright © 2009 Pearson Education, Inc. Admin: Discussion sections start tommorrow. Very useful prep for tests. You are expected to attend. From the lab TAs: try and complete your lab reports before leaving the lab (or soon after). Register for MasteringPhysics www.masteringphysics.com Course ID: MPHOLDER67874 118/132 Registered First graded assignment is posted. Due Monday 23rd

2. Copyright © 2009 Pearson Education, Inc. Resistors in Series and in Parallel How much current is drawn from the battery shown?

3. Copyright © 2009 Pearson Education, Inc. Resistors in Series and in Parallel Example: Current in one branch. What is the current through the 500-Ω resistor shown? (Note: This is the same circuit as in the previous problem.) The total current in the circuit was found to be 17 mA.

4. Copyright © 2009 Pearson Education, Inc. Resistors in Series and in Parallel Example: Bulb brightness in a circuit. The circuit shown has three identical lightbulbs, each of resistance R. (a) When switch S is closed, how will the brightness of bulbs A and B compare with that of bulb C ? (b) What happens when switch S is opened? No math required!

5. Copyright © 2009 Pearson Education, Inc. Resistors in Series and in Parallel Example: A two-speed fan. One way a multiple-speed ventilation fan for a car can be designed is to put resistors in series with the fan motor. The resistors reduce the current through the motor and make it run more slowly. Suppose the current in the motor is 5.0 A when it is connected directly across a 12-V battery. (a) What series resistor should be used to reduce the current to 2.0 A for low-speed operation? (b) What power rating should the resistor have?

6. Copyright © 2009 Pearson Education, Inc. Resistors in Series and in Parallel Example : Analyzing a circuit. A 9.0-V battery whose internal resistance r is 0.50 Ω is connected in the circuit shown. (a)How much current is drawn from the battery? (b)What is the terminal voltage of the battery? (c)What is the current in the 6.0-Ω resistor?

7. Copyright © 2009 Pearson Education, Inc. Question on next week’s assignment!!

8. Copyright © 2009 Pearson Education, Inc. An ammeter measures current; a voltmeter measures voltage. Both are based on galvanometers, unless they are digital. Ammeters and Voltmeters current is passed through a coil in a magnetic field coil experiences a torque proportional to the current. If the coil's movement is opposed by a spring, then the amount of deflection of a needle attached to the coil is proportional to the current passing through the coil. Luigi Galvani