PH 112

 

This is part of an exam I gave in the past.  I have deleted some items; mostly items which you have already seen on the quizzes, which are still “fair game”, and some which I want you to see for the first time next Thursday.  So this is a very good idea of what you will see, but it is not a complete test.

 

Please note your exam will be in class on Thursday, October 4, 2007.

Also, this is the cheat sheet you will have on your exam; you may wish to familiarize yourself with what is there and what is not.  Please note that the html conversion sometimes ruins the format and so things don’t look so nice, but it will look nice for the exam.

 

EXAM  I                                                                                                                                                                               Feb. 23, 2005

 

This exam is closed book, notes and neighbor.  You may use your calculator.  You have the regular class time to complete the exam.  As there are different versions of this test, you must put your name & color on the scantron, which must be used to record all answers.  There are 20 one pt., 20 two pt., and 10 four pt. questions.  Have a productive effort!

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D = Vt                 Vf2 = Vi2 + 2a(∆R)                Vf  =  Vi  +  at                      R = Ro + Vot  +  (1/2)at2       

sin = opp/hyp               cos = adj/hyp               tan = opp/adj                       g = 9.8 m/s2  (down)       

A = πR2           V = (4/3)πR3                  C =  2πR             F  =  qE                     eo  =  8.85 x 10-12 (mks)   

E = kq/r2      E = - ∆V/∆x      V = kq/r = EPE/q       VC =Q        

C  = KeoA/d         energy = (1/2)CV2   

proton mass  =  1.67 x 10-27                 electron mass  =  9.11 x 10-31           

charge magnitude  =  1.6 x 10-19           

Avogadro's #  =  6.02 x 1023              G  =  6.67 x 10-11  (mks)                        k  =  9 x 109     (mks)   

R  =  (rho)L/A              Watt  =  Joule/sec            Volt  =  Joule/Coul.          Kinetic Energy  =  mv2/2          

I  =  ∆q/∆t          ∆V  =  IR         P  =  IV          R(series)  =  add               R(parallel)  =  add inverses

R(series for caps)  =  add         R(parallel for caps)  =  add inverses          ∆V  =  ∆EPE/q  =  -WAB/q

                                                                                                                      

These 20 t/f questions are worth one point each.  Choices:                    

A = TRUE      B = FALSE

 

4)         The electric potential is a vector.

 

6)         Electric field lines can never cross each other.

 

11)       The resistance of a person’s total body depends greatly on the condition of their skin.

 

12)       The outer conductor of a coax cable electrically shields the inner conductor.

 

13)       When current flows through a material, heat is generated.

 

14)       It is possible for a Human Being to survive touching a metal object that had a potential of ten million volts.

 

16)       You are in your car when a large power line falls and begins sparking on your car.  You should immediately get out of your car.

 

TURN YOUR   SCANTRON   OVER

The following twenty questions are worth 2 points each—turn your scantron over.

 

51)       You are given a common meter to measure current, or an amp-meter---which is shortened to ammeter.   How should you properly use this meter?

1)         You need to break the circuit, and insert the meter in series.      

2)         You need to break the circuit, and insert the meter in parallel.   

3)         You need to break the circuit, and insert the meter in series and in parallel.

4)         You should use it in series, but not break the circuit.     

5)         You should use it in parallel, but not break the circuit.

           

 

54)       What is the ideal internal resistance of a voltmeter?

 

1)         Very small-zero.          

2)         Very large-infinity.                   

3)         The same resistance as in the circuit you are measuring.

4)         It depends on the circuit you are measuring—the ideal resistance is different for every circuit.  

 

56)       You are given 2 identical batteries and a long piece of copper wire of constant cross sectional area.  You “short” one of the batteries with a certain length of this wire, and find that the battery “dies” in one hour.  How long will the other battery last if two pieces of wire that are each twice as long are used to short the battery at the same time in a parallel configuration (as shown)?

 

I will show you something and give you some options.

 

57)       What is true about the following 3 circuits—all of the batteries and bulbs are identical.

 

1)         Each of the bulbs will light, but not with the same brightness.                       

2)         The bulb in ‘a’ will be twice as bright as in ‘c’.  

etc.

59)       You flip a switch and turn on a light.  Which combination of the following four statements is true about what happens in the connecting wire and the bulb?

various answers given, etc.

 

Even is you have never messed around with Christmas tree lights, they can be very frustrating.  On some strings of lights, if one bulb went out, they all went out. This made it very difficult to find the bad bulb.  On other “nicer” strings of lights, only that one bulb went out.    Use this information for the next 3 questions:

 

 

65)       Which of the following statements is true about two capacitors connected in parallel?  The capacitance of the capacitors differ:  C1 is not equal to  C2 . 

 

1)         The voltage across the caps are equal.              

2)         The current through the caps are equal.

3)         The charge magnitudes in the caps are equal.    

4)         The charge magnitudes in the caps are inversely related to their capacitance.

5)         The voltages across the caps are inversely related to their capacitance.

 

69)       If you could see the (Public Service electric) wires in the walls where you live, would the various outlets be wired in series or parallel?

 

1)         series.                                                   2)         parallel.

           

 

70)       As current goes through several resistors in series, it looses energy, slows down, and so the current in the circuit is getting smaller as it goes around the circuit.

 

1)         True.                                                    2)         False.  

 

 

Now for the fun part of this exam.  Please use the space provided to work out the answers to the following ten questions, and use a new scantron for your answers.

These ten questions are worth 4 points each.

 

3)         What is the value of the electric field ONE meter away from a single electron?         

 

1)  1.44 x 10-9  Volts                             3)   1.44 x 10-9  Coulombs                        5)  1.44 x 10-9  Amps

2)  1.44 x 10-9  Volts/meter                    4)   1.44 x 10-9  Coulombs/meter

 

5)         What is the total resistance of the circuit?  Neglect the R of the battery and wires.

 

I will give you a circuit and you find what is asked for.

 

6)         What is the total resistance of the circuit?  Neglect the R of the battery and wires.

 

I will give you a circuit and you find what is asked for.

 

7)         Rank order the bulbs for brightness (all bulbs and batteries are identical). 

Note:  The first answer would read; bulbs D and E are equally bright, but are dimmer than bulbs B and C, which are in turn less bright than A.

 

1)         A > B = C > D = E, etc.                                              

 

8)         Rank order the bulbs for brightness (all bulbs and batteries are identical). 

 

ditto

 

9)         An electron is superglued down and cannot move.  Another electron is placed extremely (infinitely) far away, and shot out of a gun directly towards the immovable electron.  What initial velocity would be required if you wanted the distance of closest approach to ……

 

10)       What is the total current?  Neglect the R of the battery and wires.

 

I will give you a circuit and you find what is asked for.