KCSE 2015 Electricity Paper 2 with Marking Scheme

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KCSE 2015 Electricity Paper 1 with Marking Scheme

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STATION 1
Using the components, materials and equipment provided, carry out the following tasks:
1. Connect the circuit as shown in figure 1. Let the examiner check your work. (7 marks)
2. Vary the base resistance RB to obtain each of the base current IB values shown in table 1. For each value of IB, measure and record in the table the corresponding values of VCE and Ic. (6 marks)
  Table 1
  
  I_n(μA) VCE (V) IC (mA)
  
  200
  
  220
  
  240
  
  260
  
  280
  
  300
3. Using the values in table 1:
  1. determine the current gain ß when IB = 240 u A.(2 marks)
  2. plot a graph of Ic against VcE.(5 marks)
STATION 2
Using the tools, equipment and materials provided, fabricate the saddle bracket shown in figure 2. (20 marks)
STATION 3
Using materials, components and equipment provided, perform the following tasks:
1. Connect the circuit shown in figure 3. Let the examiner check your work. (5 marks)
2. Close the switch S and adjust the power supply to obtain voltage values shown in table 2. For each voltage obtained, measure and record in the table the corresponding value of current.
  Table 2
  
  Voltage, V (V) 2.0 5.0 8.0 12.0 16.0 22.0
  
  Current, I (mA)
  
  (6 marks)
3. Using the values in table 2, draw the graph of current I against voltage V. (5 marks)
4. Determine the slope of the graph. (3 marks)
5. Name the electrical quantity expressed by the slope of the graph and name its unit. (1 mark)
STATION 4
Figure 4 shows the block diagram of the electronic circuit.

Use the equipment and accessories provided to perform the following tasks.
1. With the power supply off and output knob at minimum, connect the equipment to the terminals on circuit P as follows:
  1. Q and R, a voltmeter;
  2. S and T, a voltmeter;
  3. U and V, a milliameter;
  4. Qand R, power supply.
    (Let the examiner check your work) (4 marks)
2. Turn the power supply ON. Adjust the power supply voltage to obtain the voltage values, Es shown in Table 3.
  In each case, measure and record in table 3 the corresponding values of Load Voltage VL and load current IL.
  Table 3
  
  ES V_LOAD I_LOAD
  
  1
  
  3
  
  6
  
  7
  
  10
  
  12
  
  (9 marks)
3. Plot a graph of load voltage V, against power source voltage E_ş. (5 marks)
4. State one application of the circuit P and give the reason for your answer. (2 marks)
STATION 5
Using PVC sheated wiring, complete the installation shown in figure 5, such that the bell is operated from either A or B. (20 marks)