2. 19-6 Circuits Containing Capacitors in Series and Parallel Just as a resistor can be placed in series and/or parallel, so can capacitors. Remember Q=CV In a parallel connection of capacitors, … C eq = C 1 + C 2 + C 3 ….etc and… Q=Q 1 + Q 2 + Q 3 ….etc and… C 1 V + C 2 V + C 3 V….etc and… Q=C eq V

3. 19-6 Circuits Containing Capacitors in Series and Parallel (cont’d) In a series connection of capacitors, 1/C eq = 1/C 1 + 1/C 2 +1/C 3 …… and…. Q/C eq = Q/C 1 + Q/C 2 +Q/C 3 …… and…. V= V 1 + V 2 + V 3 …… See Page 569 diagrams See Example 19-9 p570

4. 19-8 Circuits Containing a Resistor and Capacitor RC circuits have resistors and capacitors. See diagram p570. V= e (1-e -t/RC ) The product of the resistance and capacitance is called the time constant t of a circuit.  t =RC When a circuit does not have a EMF, but is charged and the charge is released across a resistor, use V=V 0 e - t/RC See p571 diagram 19-18a See Example 19-10 p 572

5. 19-8 Heart Pacemakers One use of RC circuits is a pacemaker. A pacemaker can make a stopped heart start again…our heart has a natural pace- maker

6. 19-9 Electric Hazards; Leakage Currents Most people can feel 1mA of current. Currents above 10mA cause severe contraction of the muscles, and a person may not be able to release the device and death from paralysis of the respiratory system may occur. If 70mA or more passes through the torso or heart region for more than a second, ventricular fibrulation may occur and cause death. Dry skin has a resistance of 10 4 to 10 6 W... Wet skin has 10 3 W. I =V/R means 120 V could be lethal. See p 574

7. 19-10 DC Ammeters and Voltmeters An ammeter measures current and a voltmeter measures potential difference. The crucial part of either is the galvanometer…. A galvanometer works on the principal of the force between a magnetic field and a current-carrying coil of wire. Some of the meters on your car’s dash are connected as galvanometers.

8. The full-scale sensitivity I m, is the current needed to move the needle to the full-scale reading. An ammeter, represented by the symbol -A- consists of a galvanometer –G- in parallel with a resistor called a shunt resistor…with resistance R, while the galvanometer has resistance r. (See p 575) See Example 19-12 and 19-13.

9. HOMEWORK P 582 36-43,55-57, 60 Due Wednesday Test Thursday