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Applied Electricity 1 , May/June 2009  
Questions:   1 2   Main
General Comments
Weakness/Remedies
Strength


Question 2

(a) Connect the circuit as shown in fig 2.

(b)Ask the supervisor to check the circuit.

(c)Copy Table 3.

Table 3

Quantity

Value

V1
V2
V3
V4
         I

 

     (d) Adjust the power supply to 9 V and close switch S.

     (e)       Use the voltmeter to measure voltages V1, V2, V3,
                 and record in Table 3.
     (f)       Take the reading of the ammeter and record in Table 3.     
     (g)       Evaluate V 1 + V2.
     (h)        Evaluate  V3 + V4
     (i)         Compare the results obtained in step (g) with that obtained in step (h). 
     (j)         Evaluate     α   =  V3
                                           R3       
    (k)        Evaluate    β    =  V1
                                          R1
    (l)        Evaluate   α + β.
    (m)      Compare the results obtained in step (l) with the value of I in Table 3.

_____________________________________________________________________________________________________
Observation

The candidates were required to:

(i)         connect the circuit as shown and obtain voltage and current readings;

(ii)        calculate the voltage and current in each branch.

The expected answers were:
                                     Tables  3


Quantity

Value

V1

5.625V

V2

3.375V

V3

6.907V

V4

2.093V

I

490.6mA

                            
(g)        V1 + V2  =  (5.625 + 3.375)V  =  9v
(h)        V3 + V4  =  (6.907 + 2.093)V  =  9v
(i)         Results obtained from steps  (g)  and  (h)  were found to be the same.
(j)         I3V3 =     6.907       =  0.2093A  or  209.3mA 
                    R3              33       

(k)          I1  =  V1   =   5.625       =  0.2813A or 281.3m A
                         R1             20
(l)         I3  +  I1    =  (0.2093  +  0.2813) A = 0.4906A or 490.6mA
(m)      On comparing step (l) with the value of I, they were the same.

The candidates understood the task, they connected the resistors as required and obtained readings of the current and voltage drop.  However, some of the candidates’ readings were not correct or not expressed in the correct units.
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