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Applied Electricity 1 , May/June 2007  
Questions:   1 2   Main
General Comments
Weakness/Remedies
Strength









































Question 2

(a) Use the same circuit as for experiment 1.
(b) Close the switch Ss.
(c) Adjust the load until the ammeter reading Ip is equal to O.I2A
(d) Read and record the corresponding values of Wp and Vs.
(e) Repeat steps (c) and (d) for the values of lp as indicated in
Table 2.
(f) Copy and complete Table 2.

Vp(Volts) Wp(Watts) Vs(Volts) Ip(Amp) Vplp(Volt.Amp) Wp
VpIp

200
200
200
200
200

200

0.12
0.14
0.16
0.18
-
0.20
0.40
       

 

_____________________________________________________________________________________________________
OBSERVATION

The expected answers were:

Gradient = Wp
                 VpIp

= 24.7 – 10
75.2 – 30.05

= 0.33

(k) The gradient of the curve and the Wp values from the table are the same,
                                                                    VpIp
(l) The current in the primary when the transformer is supplying current to load is higher. The total current in primary is the phasor sum of no-load current and current in primary when the transformer is supplying current to load.
The entries in the graph depended on the readings obtained. The wrong readings got by the candidates led to their wrong graphs.
It behoves the candidates to understand how to obtain accurate readings from instruments and this will go a long way in improving their performances.



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