Physics Paper 3 Questions and Answers - Mang'u Mock 2020 Exam

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PHYSICS
PAPER 3
TIME: 2 HOURS.

Instructions to candidates

  • Answer ALL the questions
  • This paper consists of TWO Sections: A and B.
  •  ALL working MUST be clearly shown.
  • Mathematical tables and electronic calculators may be used.

Question 1

You are provided with the following apparatus:

  • micrometer screw gauge
  • clamp
  • boss
  • stand
  • optical pins
  • Copper wire
  • protractor
  • Two pieces of plasticine
  • cork

Procedure

  1. Measure the diameter of the wire using the micrometer screw gauge
    d=............cm. (1mk)
  2. Set up the apparatus as shown in the diagram below
    phycp3q2
    1. Bend the wire in the middle so as to make an angle of 40°. Attach the two small pieces of plasticine at both ends of the bend as shown in the diagram.
    2. Place the bent wire on the optical pin and give a small horizontal displacement. Note the time for 10 complete oscillations and record in the table below.
    3. Repeat the procedure above for other values of (8mks)
      Angle θº Time t for 10 oscillations (s) Period T (s) Frequency f(Hz)= 1/T f2(Hz)2 Cos(θ/2
      40º          
      60º          
      80º          
      100º          
      120º           

      1. On the graph paper provided, plot a graph of f (y-axis) against cos θ/2 (5mks)
      2. Determine the gradient S of the graph(3mks)
      3. The equation for the oscillation of the wire is given by the formula:
        f2 = 150 z cos(θ/2)
               4Π2L
        Given that the length of the wire L 15cm find the value of Z. (3mks)

Question 2

You are provided with the following apparatu

  • A mounted wire labeled N.
  • A voltmeter
  • A milliammeter
  • A switch
  • Two dry cells and two cell holders.
  • Six connecting wire with at least two crocodile clips
  • Four 1000Ω resistors labelled T.
  • A diode.

Procedure

  1. Set up the apparatus as shown below.
    1.    
      1. Connect the above apparatus as shown in the circuit diagram below with the switch S open
        phycp3q2p1
      2. With the switch S open record E the voltmeter reading (1mk)
        B= ______________________
      3. Close the switch and record V, the voltmeter reading and I, the ammeter reading (imk)
        V= ______________________(1mk)
        I= ______________________(1mk)
      4. Given that: E-V=Ir. Find for the dry cell (3mks)
  2. Now set the apparatus as shown in the set up below
    phycp3q2p2
    1. Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
      Voltmeter............................................A(1mk)
    2.  Repeat the experiment by now using x=10cm and note the readings on the milliammeter and voltmeter.
    3. Repeat ii. For other values of x and fill the table below
      Distance
      x(cm)
      0 10 20 30 40 50 60 70 80
      Current I
      (mA)
                       
      p.d (V)                  
      6 mks
    4. By using values obtained, plot a graph of current I against p.d. (5 mks)
    5. Find from the graph the value of current when p.d is 0.35V. (1 mk)

MARKING SCHEME

Question 1

  1. Measure the diameter of the wire using the micrometer screw gauge
    d=............cm. (1mk)
  2. Set up the apparatus as shown in the diagram below
    phycp3q2
    1. Bend the wire in the middle so as to make an angle of 40°. Attach the two small pieces of plasticine at both ends of the bend as shown in the diagram.
    2. Place the bent wire on the optical pin and give a small horizontal displacement. Note the time for 10 complete oscillations and record in the table below.
    3. Repeat the procedure above for other values of (8mks)
      Angle θº Time t for 10 oscillations (s) Period T (s) Frequency f(Hz)= 1/T f2(Hz)2 Cos(θ/2
      40º          
      60º          
      80º          
      100º          
      120º           

      1. On the graph paper provided, plot a graph of f (y-axis) against cos θ/2 (5mks)
      2. Determine the gradient S of the graph(3mks)
      3. The equation for the oscillation of the wire is given by the formula:
        f2 = 150 z cos(θ/2)
               4Π2L
        Given that the length of the wire L 15cm find the value of Z. (3mks)

Question 2

  1. Set up the apparatus as shown below.
    1.    
      1. Connect the above apparatus as shown in the circuit diagram below with the switch S open
        phycp3q2p1
      2. With the switch S open record E the voltmeter reading (1mk)
        B= ______________________
      3. Close the switch and record V, the voltmeter reading and I, the ammeter reading (imk)
        V= ______________________(1mk)
        I= ______________________(1mk)
      4. Given that: E-V=Ir. Find for the dry cell (3mks)
  2. Now set the apparatus as shown in the set up below
    phycp3q2p2
    1. Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
      Voltmeter............................................A(1mk)
    2.  Repeat the experiment by now using x=10cm and note the readings on the milliammeter and voltmeter.
    3. Repeat ii. For other values of x and fill the table below
      Distance
      x(cm)
      0 10 20 30 40 50 60 70 80
      Current I
      (mA)
                       
      p.d (V)                  
      6 mks
    4. By using values obtained, plot a graph of current I against p.d. (5 mks)
    5. Find from the graph the value of current when p.d is 0.35V. (1 mk)

 


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