KCSE 2014 Electricity Paper 2 Questions with Marking Scheme

QUESTIONS

EXERCISE 1
Use the circuit, equipment and component provided to perform the following tasks.

1. Connect the resistors labelled A across point X and Y of the circuit.
2. Set the stopwatch to zero.
3. Press switch S until voltage reading settles at about 10V.
4. Release push button switch S and time the duration it takes for the voltage to drop to about 3-7 V and record the time in Table 1.
   Table 1
   

   Resistor	A	B	C	D	E
   Time(s)

5. Repeat tasks (a) to (d) for each of the resistors B, C, D and E.(12 marks)
6. Use schematic symbols to draw the circuit and label the components.(6 marks)
7. From the results obtained, calculate the value of resistor labelled E.(2 marks)

EXERCISE 2
Using the materials, tools and equipment provided, fabricate the candle stand shown in figure 1. Its dimensions are given in the layout. (20 marks)

Figure 1

EXERCISE 3
Using the components, materials and equipment provided, perform the following tasks.

1. Connect the circuit shown in figure 2 and let the examiner check your work.(6 marks)
   
   Figure 2
2. Close the switch. Adjust the potentiometer to obtain voltage reading shown in Table 2. For each voltage obtained, measure and record the corresponding current values.(5 marks)
   Table 2
   

   Voltage (v)	0	0.5	0.7	0.9	1.3	1.7
   Current(mA)

3. Plot a graph of current against voltage.(6 marks)
4. From the graph:
   1. determine the resistance when the voltage is 1.3 V;
   2. give a reason for the shape of the graph.(3 marks)

EXERCISE 4
Using the pre-fabricated circuit provided in figure 3, perform the following tasks:

Figure 3

1. With the switch open:
   1. connect the milliameter between A and B. (observe the polarity).
   2. connect the voltmeter between C and D. (observe the polarity).(2 marks)
      (Let the examiner check your work)
2. Close the switch
   Adjust the variable resistor to obtain the current values in Table 3 and in each case measure and record the corresponding voltage values.(10 marks)
   Table 3
   

   Current(mA)	2	4	6	8	10
   Voltage(v)

3.                        
   1. Plot the graph of current against voltage.
   2. Use the graph to determine the value of current when the voltage is 5.5 V.(8 marks)

EXERCISE 5
Figure 4 shows a lighting circuit. Using materials, tools and equipment provided, instal the circuit such that the switch controls the lamp. (20 marks)

Figure 4

Marking Scheme