Electricity Paper 2 Questions and Answers - MECS Cluster Joint Mock Exam

QUESTIONS

1. Figure 1 shows an electrical circuit.
   
   
   1. Using the components, materials and equipment provided. Connect the circuit as shown in Figure 1 on the breadboard.
      Let the examiner check your work. (6 marks)
   2. With S1 ON, measure and record the total current IT.
      IT=………………………………………. mA (1 mark)
   3. Measure and record the currents.
      I1=………………………………………. (mA)
      I2=………………………………………. (mA)
      I3=………………………………………. (mA)
   4.        
      1. In the circuit, replace R3 with R4.
         Let the examiner check your work. (2 marks)
      2. Repeat steps (a) to (c). (4 marks)
         IT=………………………………………. (mA)
         I1=………………………………………. (mA)
         I2=………………………………………. (mA)
         I3=………………………………………. (mA)
   5.      
      1. Explain the relationship between currents I2 and I3 (2 marks)
      2. State the effect on the current IT when R3 is replaced with R4. (2 marks)
2. Using the tools, equipment and materials provided, fabricate the bracket shown in Figure 2. (20 marks)
   
   
3. Using the tools, materials and equipment provided, carry out the following tasks.
   1. Terminate the three heat resistant flexible cable to the top plug and the iron box. (15 marks)
   2. Turn the thermostat switch ‘ON’ at the maximum position. (1 mark)
   3. Measure and record the values of Resistance of the element in Table 1. (4 marks)
      

      TEST BETWEEN	READINGS OBTAINED
      1) Live and Neutral at plug 2) Live and Earth at Plug 3) Earth at Plug and Iron box body 4) Neutral at Plug and Iron box

4. Figure 3 shows the block diagram of an electronic circuit marked R.
   
   Use the equipment and accessories provide to perform the following tasks;
   1. Set the power supply voltage to 10V output.
   2. With the power supply off and switch S off, connect the equipment to the terminals of circuit R at points (+) and (-) as shown.
      1. A and B as an Ohmmeter
      2. X and Y an ammeter
      3. S and T to power supply.
         Let the examiner check your work. (3 marks)
   3. Turn the power supply ON and turn the switch ON.
      Adjust the potentiometer to obtain RL values as shown in Table 2.
   4. In each case, measure and record in table 2 the corresponding values of circuit current I and calculate values of circuit power in Watts.
      

      RL(kΩ)	I(A)	P(W)
      0 5 10 15 20 25 30 40 60 80 100

      (11 marks)
   5. Plot a graph of power against load resistance on the graph provided on the last page. (4 marks)
   6. Determine the value of load resistance that allows maximum power transfer from the graph provided in 4(e). (2 marks)
      
5. Figure 4 shows the layout of a lighting final circuit.
   
   Using PVC sheathed cable, install the circuit such that the lamp is controlled from one point. (20 marks)

MARKING SCHEME

1.        
   1. Let the examiner check your work. (6 marks)
   2. 200
   3. I1=127
      I2=73
      I3=73
   4.        
      1. Let the examiner check your work. (2 marks)
      2. IT=175
         I1=102
         I2=63
         I3=63
   5. magnitude is the same since its flowing through the same branch
2. Using the tools, equipment and materials provided, fabricate the bracket shown in Figure 2. (20 marks)

3. TEST BETWEEN	READINGS OBTAINED
   1) Live and Neutral at plug 2) Live and Earth at Plug 3) Earth at Plug and Iron box body 4) Neutral at Plug and Iron box	HIGH HIGH ZERO LOW

4. RL(kΩ) I(A) P(W)
   

   RL(kΩ)	I(A)	P(W)
   0 5 10 15 20 25 30 40 60 80 100	0 0.19 0.173 0.16 0.153 0.147 0.14 0.131 0.11 0.1 0.09	0 0.181W 0.299W 0.384W 0.468W 0.540W 0.48W 0.473W 0.47W 0.387W 0.364W

5. Figure 4 shows the layout of a lighting final circuit.
   
   Using PVC sheathed cable, install the circuit such that the lamp is controlled from one point. (20 marks)