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Electronics Paper 1, Nov/Dec 2009  
Questions: 1 2   Main
General Comments
Weakness/Remedies
Strength











































Question 1

The aim of the experiment is to examine the stabilization effect of a Zener diode.

    

  1. Connect the circuit as shown in Figure 1.
  2. Ask the Supervisor to check the circuit connection.
  3. Copy Table 1 into your answer booklet.

Vin(V)

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Vout(V)

 

 

 

 

 

 

 

 

 

  1. Switch on the d.c. power supply.
  2. Set the input voltage (Vin) to 2.0V.
  3. Measure and record in Table 1,the corresponding value of Vout.
  4. Repeat steps (e) and (f) for other values of Vin as shown in Table 1.
  5. Switch off the power supply.
  6. Draw the input voltage (Vout) on the vertical axis against the input voltage (Vin) on the horizontal axis.
  7. From the results in Table 1 and the graph, explain the stabilization effect of the Zener diode.
_____________________________________________________________________________________________________
OBSERVATION

The candidates were expected to connect the circuit as shown above, obtain the voltmeters readings, plot a graph of the output voltage against the input voltage and from the graph explain the stabilization effect of the Zener diode

The expected answers were:
                                         Table 1


Vin(V)

0

2

3

4

5

6

7

8

9

10

Vout(V)

0

2

3

4

5

6

6.3

6.3

6.3

6.3

  1. As long as the input voltage is lower than the Zener voltage of the Zener diode, the Zener diode will not influence the output voltage.

 

As soon as the input voltage becomes higher than the Zener voltage of the Zener diode, the voltage at the Zener diode or the input voltage will remain constant.

The candidates understood the task, connected the circuit and obtained readings but failed in the theory of diodes and Zener diode characteristics.

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