Friday 5 Feb:

 

 

Quiz on Monday

Quiz Equations (Electricity/Current):

 

     Description:                                              Equation:

1. Electric Force:        F       =

 

   or   F =   kq1q2 / r2

2/3. Electric Field:         E      = 

(Two Equations)

 E = k q / r2    or

4. Electric Field:         E      = 

Note: (voltage & distance)

 
   

6. Capacitance            C      =

Note: (Charge & voltage)

 

 

7. Capacitance            C      =

Note: (parallel plate capacitor)

 

8/9. Potential energy stored in a charged capacitor:      (Two Equations)

     Uc =

 

10. Resistance & Resistivity:   

                                       R  =

 

11. Ohm’s Law:

 

12/13/14

Electrical Power (electrical circuit):                        P   =

   or     or   V2/R

15. Capacitors in Series:   Cs  =

Cs =  (C1) (C2)  / (C1) + (C2) or

 

16. Capacitors in Parallel:  Cp =

Cp =∑i Ci

17. Resistors in Series:   Rs  =

 

18. Resistors in Parallel:  Rp =

Rp = (R1)(R2)/(R1)+(R2)or   

19. Elect Potential (with Elect Field):

                                     V =

 V = E d   

  20. Coulomb Constant:  k =

 K= 1 / 4peo

 

 

Pre-Test 15-18

(Pre-Test)    Understanding Concepts: Electric Circuits

       Name ___________________________

 

 

 

 

 

[Schematic Symbol]1.                20V                                   

 

 

[Schematic Symbol][Schematic Symbol]                    R1 = 4W     R2 = ?

                V1 = -12V              V2 = ?

 

Find:     a.   V2

b.      Current through R1

c.       Current through R2

d.      R2

e.       Total Resistance of circuit

f.        Direction of Current (CW or CCW)

g.       Power output of R1

h.       Power output of R2

i.         If R’s were light bulbs, which one is brighter?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Schematic Symbol]                31V                                      

 

                                                                                               

       [Schematic Symbol][Schematic Symbol][Schematic Symbol][Schematic Symbol]I2 = 5.0A                  I3 = 3.0A                               R4 = 1.5W     

   R1 = 3W                                                                              R3      

[Schematic Symbol]                                          R2                                                    R5

      V5 = -6V

2.        a.   V1

b.      Current through V5

c.       R5

d.      V3  &  V4

e.       R2 

f.        Power output of R2

g.       Total Resistance of circuit

h.       If R’s were light bulbs, list order of brightness (Brightest bulb to dimmest)

 

3.

3.

        EMF2 = 6.0V            EMF3 = 10.0V

                  R2 = ?                R3 = 1.0W     R4 = 4.0W                           

 

            V2 = ?V     P          V3 = ?V            V4 = ?V     

 

                                               

                        V1 = ?V

                                                I = 3.0Amps

              EMF1 = 20.0V

                    r1 = 1.0W    

a.   V1

b.      V2

c.       V3

d.      V4

 

e.       Find the internal resistance of the 6.0V cell

 

 

f.        Electrical Potential at Point P (assume “0” just to the right of EMF1)

 

4.

                V1= ?           R2= ?            Power 2 =  20W

 

5.0Amps       R1 = 2.0W              R3= ?

                                     V3= 6V

                                                  3.0Amps   

Find:

a.       V1=

b.      R3 =

c.       R2 =

d.      Total power used by this circuit

 

 

                      

 

                      

5.                     Q1 = 6.0F                             V2 = ?V             Q2 = 1.0F         

                                               

 

                           V1 = ?V

 

                                                                            Q3 = 3.0F       

                                                                            V3 = ?V

 

 

                        VBat = 5.0V

  Find:

a.   V1

b.  V2

c.  V3

d. Q1 

e. Q2

f. Q3

 

 

 

6.             Find: a. Current through motor (100% efficient).      

 b. Current through motor (70% efficient).        

 

 

       VBat = 16V                        Electrical Motor

 

 

                        .

The motor lifts the 4.0-kg block 3.0m in 2.0 sec.                                                4.0-kg 

Moving at constant Velocity

 

7. If you have a 12V battery in series circuit with a 0.5 F capacitor and 3.0 W resistor.

Find the following:

a. Initial current 

b. Current after a period of time 

c. Voltage on Capacitor after a period of time  

d. Charge on the capacitor

 

 

(Q#8): You have a 12V battery that is connected to 3 parallel lines.

Line 1:  Bulb A = 2 W’s     

Line 2:  Bulb B = 4 W’s 

Line 3:  (Two Bulbs) Bulb C = 2 W’s &  Bulb D = 4 W’s.

 

8. Find:  Rank in order of brightness (From brightest to dimmest)

 

                       

 

Questions 9 -12  refer to the circuit shown to the right.

 

9. The equivalent capacitance for this network is most nearly

 

(A) 10/7 uF

(B) 3/2 uF

(C) 7/3 uF

(D) 7 uF

(E) 14 uF

 

10. The charge stored in the 5‑microfarad capacitor is most nearly

 

(A) 360 uC

(B) 500  uC

(C) 710 uC

(D) 1,100 uC

(E) 1,800 uC

 

11. The voltage drop in the 3‑microfarad capacitor is

 

(A) 33.3 V

(B) 50.0  V

(C) 66.7 V

(D) 25.0 V

(E) 75.0  V

 

 

 

 

12. The PE stored on the top 5.0‑microfarad capacitor is

(A)   500 uJ

(B)  5,000  uJ

(C)  0.2  uJ

(D)  5 x 10-2 J

(E)  20  uJ

 

13. The second of two capacitors has twice the charge and half the voltage. The capacitance of the second is

    1. equal to that of the first.
    2. twice that of the first
    3. four times that of the first
    4. one-fourth that of the first.
  1. IF you place an uncharged conducting sphere in a uniform electric field?

a.  The net force will be in the direction of the field                                             

b. The net force will be in the opposite direction to the field 

c. The charge the outside and inside will both be positive.

d. The charge the outside and inside will both be negative.

e. The net force on it will be zero

 

15. A parallel-plate capacitor is charged by connection to a battery.  If the battery is disconnected and the separation between the plates is increased, what will happen to the charge on the capacitor and the voltage across it?

(A)   Both remain fixed.

(B)    Both increase.

(C)    Both decrease.

(D)   The charge increases and the voltage decreases.

(E)    The charge remains fixed and the voltage increases.

 

16. Two parallel conducting plates are connected to a constant voltage source.   The magnitude of the elec­tric field between the plates is 2,000 N/C.   If the voltage is doubled and the distance between the plates is reduced to 1/5 the original distance, the magnitude of the new electric field is

 

a. 800 N/C           b. 1,600 N/C           c. 2,400 N/C           d. 5,000 N/C           e. 20,000 N/C

 

17. A positive charge is placed on an insulated solid conducting sphere. Which of the following is true?

 

   (A) The charge resides uniformly throughout the sphere.

   (B) The electric field inside the sphere is constant in magnitude, but not zero.

   (C) The electric field in the region surrounding the sphere increases with increasing distance

         from the sphere.

   (D) An insulated metal object acquires a net positive charge when brought near to, but not in

          contact with, the sphere.

   (E) When a second conducting sphere is connected by a conducting wire to the first sphere,

          charge is transferred until the electric potentials of the two spheres are equal.

(Q’ s  18-19): A point P is 0.20 meter from a point charge of 1.1 x 10-7 coulomb.

 

  1. The intensity of the electric field at point P is most nearly

(A)   1.0 x 104 N/C

(B)    1.0 x 103 N/C

(C)    2.5 x 104 N/C

(D)   2.5 x 103 N/C

(E)    2.5 x 102 N/C

 

  1. Text Box:  

     

    The electric potential at point P is most nearly

(A)   2.0 x 10-3 V

(B)    2.0 x 101 V

(C)    5. 0 x 102 V     

(D)   5.0 x 103 V

(E)    5.0 x 104 V

 

 

  1. A 4 capacitor is charged to a potential difference of 100 V. The electrical energy stored in the capacitor is

 

(A)    

(B)    

(C)    

(D)    

(E)     

 

 

 

The figure below shows two particles, each with a charge of +Q, that are located at the opposite corners of a square of side d.

Text Box: Q21 & 22

 

 

 

 

 


 

21.  What is the direction of the net electric field at point P ?

  

(A)            

 

(B)            

 

(C)          

  

 

(D)            

 

(E)           

  

 

 

 


     
  1. What is the potential energy of a particle of charge +q that is held at point P?

 

a.     Zero

      b.

 

 

c.

 

      d.

 

 

e.

 

 

 

  1. What is the speed of an electron that is accelerated from 8,000 to 30,000 Volts?

(A) 9 x 107 m/s

(B) .9 x 109 m/s

(C) 8.8 x 109 m/s

(D) 88 x 109 m/s

(E) 9 x 106 m/s

 

  1. Voltage Law around a closed loop:

 

 

 

 

  1.  Current Law entering/leaving a junction:

 

 

 

 

 

26. Capacitor 1 has capacitance C1 and voltage V1. Capacitor 2 has four times the capacitance and the same voltage. Its energy U2 equals

    1. U1
    2. 2U1
    3. 4U1
    4. 8U1
    5. 16U1

27.  You have three capacitors C1= 20 mF, C2=  60  mF and C3= 25 mF.

How can you arrange them to get an equivalent capacitance of  16.2mF.

a.                               b.   

 c.                                          d.

 

28. Capacitor 1 has capacitance C1 and voltage V1. Capacitor 2 has three times the voltage and the same capacitance. Its energy U2 equals

    1. U1
    2. 3U1
    3. 6U1
    4. 9U1
  1. Two capacitors have the same capacitance but the second has twice the charge of the first. Its stored energy is
    1. equal to four times that of the first
    2. equal to twice that of the first.
    3. equal to the energy of the first one
    4. equal to eight times that of the first
  2. The second of two capacitors has twice the charge and half the voltage. Its energy is
    1. equal to that of the first one
    2. twice that of the first.
    3. four times that of the first.
    4. six times that of the first.
  3. A solid conducting sphere is given a positive charge Q.  How is the charge Q distributed in or on the sphere?

(A)   It is concentrated at the center of the sphere.

(B)    It is uniformly distributed throughout the sphere.

(C)    Its density decreases radially outward from the center.

(D)   Its density increases radially outward from the center.

(E)    It is uniformly distributed on the surface of the sphere only.

 

 

 

 

Electricity III



 

Top of Form

1.) If a current of 3 A is divided by the following circuit, the current flowing through the 4 Ohm resistor is …

1 

3 A

2 

2 A

3 

1,5 A

4 

1 A

 pmcelec1.gif 

 

2.) The diagram at the right shows part of a circuit into which a current I is flowing. Which ammeter shows the highest reading?

1 

A1

2 

A2

3 

A3

4 

All three ammeters give the same reading

pmcelec2.gif

 

3.) The diagram to the right represents a part of a circuit containing an ohmic resistor, a voltmeter and an ammeter. If the reading on the ammeter A increases the reading on voltmeter V …

1 

increases in the same ratio.

2 

increases, but not in the same ratio.

3 

remains unchanged.

4 

decreases in the same ratio.

 

pmcelec3.gif

4.) A battery is connected to two identical light bulbs in parallel as well as another identical bulb in series. An ammeter and a voltmeter are also connected as shown in the circuit diagram below.

pmcelec4.gif

One of the light bulbs connected in parallel is unscrewed. How will the ammeter and the voltmeter readings change?

 

   Voltmeter reading   

   Ammeter reading   

1 

increases

increases

2 

increases

decreases

3 

increases

unchanged

4 

decreases

decreases

 

5.) A learner connects a circuit as shown in the diagram to the right. He/she uses a source of electricity with an electromotive force (emf) of 12 V.   Which one of the following best gives the ammeter and voltmeter readings which the learner is most likely to get with this circuit?

 

Ammeter reading

Voltmeter reading

1 

reads zero

reads zero

2 

reads zero

reads 12 V

3 

very large reading

reads zero

4 

very large reading

reads 12 V

pmcelec5.gif

 

 

 

 

 

 

 

6.) Three identical resistors of 4 W are connected to give a combined resistance of 6 W. Which of the following circuit diagrams illustrates how this was done?


 

1 

I

2 

II

3 

III

4 

IV

      pmcelec6.gif

 

7.) In the circuit to the right B1, B2 and B3 are identical light bulbs. The internal resistance of the battery can be ignored.
Which statement is true regarding the relative brightness of the bulbs?

1 

The three bulbs glow with the same brightness.

2 

B2 and B3 glow with the same brightness but brighter than B1.

3 

B2 and B3 glow with the same brightness but less brightly than B1.

4 

B1 glows brighter than B2 while B2 in turn glows brighter than B3.

  pmcelec7.gif

 

8.) Two identical light bulbs, X and Y, are connected in series as shown in the sketch to the right.
How will the brightness of the bulbs change if switch S is closed?

  

X

Y

1 

brighter

brighter

2 

dimmer

dimmer

3 

brighter

not lit up

4 

not lit up

brighter

  

pmcelec8.gif

 

 

 

 

9.) A student connects three identical resistors as shown in the sketch to the right.
The potential difference across the battery is 12 Volt. What are the readings on V1 and V2 respectively?

 

V1

V2

1 

4

8

2 

6

6

3 

8

4

4 

9

3

 pmcelec9.gif 

10.) A 9 V battery is composed of six 1,5 V cells, which are connected in series. Each cell has an internal resistance of 0,2 W. What is the highest current that can be obtained from such a battery?

1 

7,5 A

2 

1,5 A

3 

1,2 A

4 

0,3 A

 

Top of Form

11.) Which one of the circuits shown in the diagram below can be used to determine the resistance of R?

1 

I

2 

II

3 

III

4 

IV

              electricity III, diagram 1

 

12.) A car's starter motor draws a current of 100 A at 12,0 V when starting the engine. The mechanical power required to turn the engine is 960 W. At what rate is energy from the battery converted to non-mechanical forms of energy?

1 

240 W

2 

960 W

3 

1200 W

4 

1440 W

13) In the circuit shown below one of the bulbs blew. The result was that all bulbs stopped glowing. Which bulb blew?

1 

bulb a

2 

bulb b

3 

bulb c

4 

bulb d

 

electricity III, diagram 2

 

 

14.) Three resistors are connected to a battery as shown in the diagram. At which point in the circuit is the current the smallest?

1 

a

2 

b

3 

c

4 

d

electricity III, diagram 3

 

 

 

 

15.) In the circuit shown, the resistance of the ammeter, the battery and the connecting wires are negligible. The voltmeter has a very high resistance. The ammeter reads 1,5 A. What is the reading on the voltmeter?

1 

4 V

2 

6 V

3 

8 V

4 

12 V

electricity III, diagram 4

16.) Two resistors are connected in parallel as shown in the diagram. The current flowing through the ammeter is:

1 

0,6 A

2 

1,5 A

3 

2,5 A

4 

14,4 A

electricity III, diagram 5

17.) Consider the circuit shown to the right. If switch S is closed, the readings on the voltmeter and ammeter will change as follows:

 

voltmeter reading  

  ammeter reading

1 

becomes zero

remains the same

2 

becomes zero

increases

3 

remains the same

decreases

4 

decreases

increases

   electricity III, diagram 6

18.) The circuit below shows two identical bulbs, L and M, which are connected to a battery and a variable resistor R. How will the brightness of the bulbs be affected if the resistance of R is increased?

 

  bulb L  

  bulb M 

1 

dimmer

brighter

2 

dimmer

dimmer

3 

dimmer

the same

4 

brighter

the same

         electricity III, diagram 7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The information given in the box refers to questions 19 and 20:

The battery in the circuit has an internal resistance r and an emf E. The resistance of the ammeter and the conductors is negligible and the voltmeter has a high resistance

 

19.) When the switch S is closed, the …

 

   voltmeter reading   

   ammeter reading   

1 

decreases

decreases

2 

decreases

increases

3 

increases

decreases

4 

increases

increases

 

 

 

20.) When the switch S is closed the power in the resistors R1 and R2 …

 

   power in R1   

   power in R2   

1 

decreases

decreases

2 

decreases

increases

3 

increases

decreases

4 

increases

increases

 

Top of Form

21.) Consider the electric circuit shown in the diagram at the right.     The reading on the voltmeter V is ...

A

0 V

B

2 V

C

4 V

D

6 V

 

electricity II, diagram 1

22.) Two light bulbs P and Q are identical in all respects, except that P's filament is thicker than Q's. If the same potential difference is applied to each, then …

A

P will burn brighter because it has the greater resistance.

B

Q will burn brighter because it has the greater resistance.

C

P will burn brighter because it has the lower resistance.

D

Q will burn brighter because it has the lower resistance.

 

23.) The ammeter and the battery in the sketch to the right have negligible resistance. The resistors are in parallel. What will happen to the ammeter and voltmeter readings when switch S is closed?

 

ammeter reading

voltmeter reading

A

increases

unchanged

B

increases

increases

C

decreases

decreases

D

decreases

increases

 

electricity II, diagram 2

 

 

 

24.) In the circuit shown the bulb marked 2R has twice the resistance of the bulb marked R. Compared with bulb 2R, the current in bulb R and its brightness compared to the other bulb, is …

 

current in R

brightness in 2R

A

larger

brighter

B

larger

dimmer

C

smaller

brighter

D

smaller

dimmer

 

electricity II, diagram 3

 

 

 

 

25.) A student connects four identical light bulbs in a circuit as shown to the below. They observe that the brightness of bulb A varies if some of the switches are closed. In which case will bulb A burn brightest?

A

S1 closed with S2 and S3 open

B

S1 and S2 closed with S3 open

C

S1, S2 and S3 closed

D

S1, S2 and S3 open

electricity II, diagram 4

26.) Two identical light bulbs X and Y, which are rated at 60 W; 240 V, are connected in series to a 240 V source as shown in the diagram below. If point A in the circuit is now connected to point B by a piece of copper wire with very low resistance, how will the brightness of each bulb change?

A

Both X and Y will burn brighter.

B

Both X and Y will burn less brightly.

C

X will burn brighter and Y will not burn.

D

Y will burn brighter and X will not burn.

electricity II, diagram 5

27.) A battery is connected to a small lamp. If a second identical lamp is connected in series with the first, what will happen to the current provided by the battery?

A

it will decrease

B

it will remain the same

C

it will increase

D

it will become zero

 

28) A 200 V electrical outlet is protected by a circuit breaker. The circuit breaker will cut out if the current drawn from the outlets exceeds 16 A. A 1000 W toaster and a 2000 W kettle can be connected to the outlet, either singly, or both in parallel using a double adapter. Which use of the appliances will trip the circuit breaker?

 

A

the toaster used on its own

B

the kettle used on its own

C

the toaster and the kettle together

D

none of the above

electricity II, diagram 6

29.) Two light bulbs in parallel are marked 230 V; 75 W and 230 V; 150 W. If the first bulb has a resistance R, then the resistance of the second is …

A. ¼ R                         B. ½ R             C. 2 R              D. 4 R

30.) Two resistors of resistance 2R and 3R are connected in series with a battery, which has an emf of E and an internal resistance R. What is the potential difference across the resistor of resistance 2R?

A

E/3

B

2E/5

C

E/2

D

2E

electricity II, diagram 7

Bottom of Form

 

 

 

 

 

 

 

 

 

 

 

 

 

1.    (2)

11.  (4)

21.B

 

2.    (4)

12.  (1)

22.C

 

3.    (1)

13.  (3)

23.A

 

4.    (2)

14.  (3)

24.B

 

5.    (2)

15.  (2)

25.C

 

6.    (2)

16.  (3)

26.D

 

7.    (3)

17.  (2)

27.A

 

8.    (4)

18.  (1)

28.D

 

9.    (3)

19.  (2)

29.B

 

    10.  (1)

20. (3)

    30. A