PHYSICS PAPER 3 - 2019 LAINAKU JOINT MOCK EVALUATION EXAMINATION

 

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. 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)
     2. Connect the circuit as shown in figure 1 below.
        
     3. Close the switch and note the maximum voltage attained on the voltmeter. Record it as V_max
        V_max=.......................................................... V           (1 mark)
     4. 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.
     5. 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 T_av2mks
     4. Given that T_av=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.
        
        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
        

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