waecE-LEARNING
Basic Electricity Paper 3 , Nov/Dec 2014  
Questions:   1 2   Main
General Comments
Weakness/Remedies
Strength





















Question 2

AIM: To verify Ohm’s law in a series d.c circuit.

                                          VS = 5 V


Quantity

Measured value

RT

 

Total current, IT

 

Supply voltage

 

VR3

 

VR4

 

           

 

 

Table 3          
                                              
                                               VS = 10 V


Quantity

Measured value

RT

 

Total current, IT

 

Supply voltage

 

VR3

 

VR4

 

                                                                                                           
 

 

  1.   Adjust the power supply to 5 V.
  2.   Close switch S.
  3.   Measure the total resistance RT and record in Table 2.
  4.   Measure the supply voltage across PQ and the voltage drop across each of

  the resistors R3 and R4 and record the results in Table 2.

    •   Read and record in Table 2 the ammeter reading (IT).
    •   Open switch S.
    •   Adjust the power supply to 10 V.
    •   Repeat steps (e) to (i) and record all the readings in Table 3.
    •   Compare (VR3 + VR4) (V) with Vs(V) in Table 2.
    • Compare (R3 + R4) Ω with RT Ω in Table 3.
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Observation

The candidates were expected to connect the circuit as shown in Figure 1, measure and record in Tables 2 and 3 the expected readings. They were also required to evaluate some quantities and do some comparisons.
The expected answers were:
 (c)                                           Table 2          
                                              
                                               VS = 5 V


Quantity

Measured value

RT

2174 Ω

Total current, IT

2.30 mA

Supply voltage

5V

VR3

2.25 V

VR4

2.75 V

                                                                                                           
 

 

                                                           

Table 3          
                                              
                                               VS = 10 V


Quantity

Measured value

RT

2.2 kΩ

Total current, IT

4.60 mA

Supply voltage

10 V

VR3

4.50 V

VR4

5.50 V

                                                                                                           
 

 

 

(l)         The two voltages are same                                                                
            (m)       The two resistances are same                                                             
Candidates did well in this question. Majority of them obtained more accurate readings than in Question 1.

 

 

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