Physics P3 Questions and Answers - Nambale Mock Exams 2021/2022

Instructions to candidates

• Write your name, index number, school and date in the spaces provided above
• Sign and write the date of the examination in the spaces provided above
• Answer all the questions in the spaces provided
• All writings must be shown in the spaces provided

FOR EXAMINER’S USE ONLY

Question

Question One
You are provided with the following

• Two cells of 1.5V each
• Nichrome wire labeled W mounted on a metre rule
• An ammeter (0 – 1.5A) or (0 - 2.5A)
• A cell holder
• Voltmeter (0 – 5V)
• 8 connecting wires atleast 4 with crocodile clips (or a jockey)
• A switch
• A metre rule

Proceed as follows:

1. Connect the circuit as shown in the figure 1 below.
   
   Figure 1
2.                          
   1. Connect the end of A and point B when AB = 100cm across the terminals as shown in the figure 1 above.
      Close the switch and measure both current I and p.d, V across the wire AB
      Current I....................... A
      P.d, V........................ V
   2. Measure the emf of the cell, E = V
3. Reduce the length AB as shown, 100cm, 70cm, 60cm, 50cm, 40cm, 30cm and 20cm. In each case record the current (I) and the corresponding values of p.d (V)
4. Enter the length as shown in the table 1 below:
   

   Length AB (cm)	100	70	60	50	40	30	20
   Current I (A)
   p.d (V)
   E – V (V)

   Table 1
5. Complete the table
   1. Plot a graph of (E – V) against I (A)
   2. Determine the gradients of the graph
      
      Given the equation, E = V =Ir, determine the internal resistance of each cell (3mks)

Question Two
Part A
You are provided with the following apparatus

• A wooden metre rule
• 10cm long cotton thread
• Masses, two of 10g and two of 20g
• Knife edge – 20cm high

Proceed as follows

1. Arrange the apparatus as shown in figure 2 below
2. Balance the metre rule on the edge and adjust the metre rule until it balances horizontally when there is no mass on it. The knife edge is now at the position of (cog)
3. Record the position of (cog)
   Position of c.o.g = ..................................cm
   Figure 2
   
4. Now hang a mass on the metre rule by use of the thread at 1cm mark. Adjust the knife edge until the metre rule balances again at new mark. Record the length d1 and the corresponding length d2.
   1. Repeat the procedure for different masses and complete the table 2 shown below.
      Table 2
      

      Mass, m(g)	10	20	30	40	50	60
      Distance d1 (cm)
      Distance d2 (cm)
      Mass (m) x distance d2 =md2

   2. Plot a graph of md2 against d1 (5mks) 
      
   3. Calculate the slopes of the graph (2mks)

Part B
You are provided with the following apparatus

• A lens
• A lens holder
• A candle
• A white screen
• A metre rule

Procedure
e). Set up the apparatus as shown in the figure 3 below:

f). Starting with u = 30cm adjust the position of the screen to obtain a sharp image of the candle. Record value of V in the table shown below:
g).               

1. Repeat the procedure above for u = 20cm and complete table below:
   Table 3
   

   u (cm)	v (cm)	M = v/u
   20
   30

   (2mks)
2. Given that the focal length of the lens satisfies the equation,  determine the average value of the focal length

MARKING SCHEME

Question One

1.                    
   1. I = 0.5 ± 0.05A  1⁄2 mk
      p.d = 2.50 ± 0.2V  1⁄2 mk
   2.  e.m.f, E = 3.0V ± 0.2 1 mk
2.                    
   

   Length AB (cm)	100	70	60	50	40	30	20
   Current (A)	0.50	0.60	0.65	0.70	0.75	0.80	0.90	± 0.05
   p.d (V)	2.50	2.30	2.25	2.15	2.10	2.00	1.90	± 0.2
   E – V (V)	0.50	0.70	0.75	0.85	0.90	1.00	1.10

3.                                                         
   1.  Graph
      • Axis labeled with units
      • Scale: uniform and simple
      • 4 correctly plotted points
      • Line through at least 3 correctly plotted points
        Total 5mks
   2. Gradient
      =∆Y
        ∆X
      =∆(E-V)
            ∆I
      =0.5
        0.3
      =5=1.67 V
        3          A
      Internal substitution
      Correct evaluation
      Accuracy
      Total 3mks
      NB: No line no slope
      

Question Two
Part A
(c) c.o.g = 50.0 ± 0.5 1
(e) (i)

• Axis labeled with units (1mk)
• Scale simple and uniform (1mk)
• Atleast 4 correctly plotted points (2mks)
• Line through atleast 3 correctly plotted points (1mk)
  Total marks 5mks

(iv) Gradient
=∆Y
  ∆X
=(∆md²)
  (∆d¹)
=(360-444)
   (12.4-4)
=(-84)
    8.4
=-10

• 1 Evaluation
• 1 answer
  Total 2mks

f=v/(1+m)=60/(1+3)=10cm+2cm
f=v/(1+m)=30/(1+1)=15cm+2cm 
Average Value=(15+15)/2
=15cm±2cm

CONFIDENTIAL

Question One

• Two dry cells of 1.5V each.
• Nichrome wire labeled W mounted on a metre rule.
• An ammeter (0-1.5A) or (0-2.5A)
• A cell holder.
• Voltmeter.
• 8 connecting wires atleast 4 wash crocodile clips (or a Jockey)
• A switch.
• A metre rule.

Question Two

• A metre rule
• 10cm long cotton thread.
• Two masses of 10g.
• Two masses of 20g.
• Knife edge, 20cm high.
• A candle.
• A lens holder.
• A white screen.
• Converging len of focal length 15cm.