Chapter 9 - Macro eletricity

 

Why convention current (I) instead of electron current, voltage (V) instead of electric field, resistance (R) instead of mobility?

 

Because thatÕs what commercial meters read.

 

Conventional current flows from high voltage to low voltage.

 

i = nAv = number of charge carriers per second.  If q = charge per carrier.

I = qnAv = charge per second or

 

9.1.2a sis called conductivity of medium & s  =qnu

                       NOTE   

9.1.4               Do the aquarium demo!

9.1.5              

                       Resistance

                       Where resistivity , which is temperature dependent.

                       NOTE: V causes current, so I is the dependent variable in

                       which is usually written as DV=IR and is called OmhÕs Law.

DO 9.1.5b+c A little conventional drill and practice. Do it! 

9.1.6               OhmÕs materials - where r is assumed constant.   .

                       Batteries and capacitors are not ohmic devices.

DO 9.1.6 a+b           

9.2                      has units of volts; but is NOT a potential difference because it does NOT vary.

 

Examine the Ōloop analysisĶ page 349 carefully.

U do 9.2.2a!  ItÕs important for understanding later work in Kirk HoffÕs Laws.

DO 9.2.2b

U do 9.2.2c.

 

9.3.1               The Loop Rule- comes from energy conservation.

                       See fig pg 353

                       SDVÕs = V2 - V3 + V1 - V2 + 0 -Vb = 0

                       +IR2 + IR1 - Vb = 0

                      

 

DO 9.3.1a      Important!  Discuss.

9.3.2               The node rule - comes from current conservation.

                       If Iin> 0, Iout< 0m then Snode = 0

DO 9.3.2 a + b.

9.3.3              

                        do 9.3.3 a, b, c.

DO 9.3.3 a&b

DO 9.3.3c      (214 0nly)       Energy stored in a capacitor: Uc = work done in charging it =                       

9.4.1               A battery has internal resistance.

                       Can be thought of as battery in series with a resistor.

      is really      

           ideal: emf - IR = 0                                           actual: emf - Ir - IR = 0

                                                                                               I= emf / (r+R)

DO 9.4.1 a

DO 9.4.1 b, c, d (214 only)

9.4.2               Experimental evidence-

                       9.4.2 a, b, c    WeÕll do this only if we have old batteries!

 

RBD              For conventional current use right hand rule instead of left hand rule.

9.4.3               D C circuits.  KirkhoffÕs Laws.  My method.

                       Do probs from text and their probs pg 361, and pg 897 from Serway.

DO  9.4.3 c plus one from Serway text.

DO 9.4.4 a - f

9.4.4   Do a sum up   

           Resistors in Series.                                          CapÕs in series.

          

           Resistance in parallel.                                      CapÕs in Parallel.

 

9.5 Read!  To help prevent meter murder.