PHYSICS PAPER 3 - 2019 LAINAKU JOINT MOCK EVALUATION EXAMINATION

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  1. PART A
    You are provided with the following:
    • a voltmeter (0 – 5V)
    • a carbon resistor labelled R
    • Two new size D dry cells
    • cells holder
    • a capacitor labelled C (2200µF)
    • a stopwatch
    • eight connecting wires at least four of which have crocodile clips
    • a switch
      Proceed as follows :
        1. Draw a circuit diagramhaving a switch, voltmeter, two dry cells and connecting wires that can be used to determine the Emf of the cells provided. (1mk)
        2. Use the above circuit to determine theEmfof the cells
          Emf =................................................................V(1mk)
      1. Connect the circuit as shown in figure 1 below.
        phyc3 part1111
      2. Close the switch and note the maximum voltage attained on the voltmeter. Record it as Vmax
        Vmax=.......................................................... V           (1 mark)
      3. Open the switch and simultaneously start your stopwatch and note the time taken for the voltmeter reading to decrease from V max to 0.2V. record this value in table 1 below. Short the terminals of the capacitor C to attain a reading of zero volts on the voltmeter.
      4. Repeat procedure iii and iv for the other values of the voltage indicated in table 1

        Voltage, V (volts)

        0.2

        0.5

        0.8

        1.0

        1.5

        1.8

        Time (t)(s) taken for voltage to decrease from V maxto V

                   
        determine the resistance R of the resistor given that t =70/11CR. Where t is the time at which V=0.5V and C is the capacitance of the capacitor. 3mks  
  2. PART B
    You are provided with:
    • A complete stand
    • A stop watch
    • A light string
    • A pendulum bob or a 50g mass
    • A metre rule or a half metre rule
      Proceed as follows:
      1. Set up the apparatus as shown in the figure below
      2. Displace the bob slightly at a small angle from the vertical line and record the time taken 20 oscillations in the table below. Repeat the for two more trials

        Trials

        Trial 1

        Trial 2

        Trial 3

        Time for 20 oscillations

             
        Find the average time for 20 oscillations                                           1 ½ mks    
      3. Calculate the average periodic time Tav2mks
      4. Given that Tav=2π find the value of g                                       3mks
  3. PART C
    You are provided with the following:-
    • A biconvex lens.
    • A lens holder.
    • A screen.
    • A meter rule.
    • A candle
    • A cross wire
      Proceed as follows:
      1. Set up the apparatus as shown in the figure below.
        phyc3 part2222
        NB: THE CROSS WIRE PROVIDED MUST BE PLACED JUST INFRONT OF THE      CANDLE TO ACT AS THE OBJECT     
      2. Place a lit candle and a cross wire at a distance U = 20cm from the len
      3. Adjust the position of the screen until a sharp image of the cross wire is focused on the screen. Record d in the table 2.
      4. Repeat part (b) and (c) for other values shown in table 2 and complete the table. (8mks) 

        U(cm)

        20

        25

        30

        35

        40

        45

        D (cm)

                   

        V=D-U(cm)

                   

        1/m =u/v

                   
        determine the slope S of the graph             (3mks)Plot a graph of 1/m against U. (5mks)
      5. given that 1/f=1/v +1/u,   use the graph to determine the focal length of the lens4mks
        phyc3graph


MARKING SCHEME

1. i)a

b)

i

v

vi

i

v

 

d

e

f

g

QUESTION ONE

PART A 

Emf………………..3.0V ±0.1           correct to 1 dp

V max..................................2.5 V±0.1correct to 1 dp

Voltage, V (volts)

0.2

0.5

0.8

1.0

1.5

1.8

Time (t)(s) taken for voltage to decrease from V maxto V

23.72

 14.03

 10.16

 8.12

 4.78

 3.07

Correct substitution                             1mk

Correct evaluation                                 1mk

Correct answer within 1000±50Ω with correct units 4sf   1mk

NB ½ MARK FOR NO UNITS, NO MARK FOR WRONG UNIT

PART B

Trials

Trial 1

Trial 2

Trial 3

Time for 20 oscillations

     

Answers within       29.94   ±3s

1/2mk for the principle of averaging  

1 mk for correct answer using the learners values

NB ½ MARK FOR NO UNITS, NO MARK FOR WRONG UNIT

Tav =answer in vi above ÷20           1mk correct substation 1mk correct answer

NB ½ MARK FOR NO UNITS, NO MARK FOR WRONG UNIT

Correct substitution     1mk    

Correct evaluation       1mk

Correct answer             1mk          

QUESTION 2

U(cm)

20

25

30

35

40

45

D (cm)

75.0

62.0

60.0

62.0

64.0

 

V=D-U(cm)

           

1/m =u/v

           

Axis       (1mk)   both well labeled with units

Scale     (1mk)    simple and uniform

Plotting (2mks)   each correctly plotted point within 1 small square

 ½ a mark a maximum of 4 pts

Curve   ( 1mk)   a smooth curve through at least four correctly plotted pts

Change in y                                           1 mk

Change in x                                           1 mk

Correct evaluation with correct units   1mk    

NB ½ MARK FOR NO UNITS, NO MARK FOR WRONG UNIT

Rearranging 1/f =1/v+1/u to u/v=u/f-1   (1mk)

Identifying that slope =1/f                       (1mk)

Correct evaluation           1mk

Answer with correct units      1mk     within     15±2 cm

NB ½ MARK FOR NO UNITS, NO MARK FOR WRONG UNIT

1 mk

1mk

1mk

6 mks each correct value 1mk ±3.0 s

Correct to 2dp

3mks

1½mks

2dp a must

1 ½mks

2mks

3mks

20MKS

(1mk) for each correct value

(1mk) for all correct values

(1mk) for all correct values

8 mks

5mks

3mks

4mks

20mks

 


                                                                                   

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