250+ TOP MCQs on Characteristics of Potential Transformers and Answers

Electrical Measurements & Measuring Instruments Multiple Choice Questions on “Characteristics of Potential Transformers”.

1. Increasing secondary burden _____________
a) increases I_s
b) decreases I_s
c) keeps I_s constant
d) decreases I_p
Answer: a
Clarification: When the secondary burden of a potential transformer increases, it leads to an increase in the secondary current. As a result the primary current also increases.

2. For a given V_p the V_s __________
a) increases
b) decreases
c) remains constant
d) depends on the supply
Answer: b
Clarification: For a particular value of primary voltage V_p, the value of the secondary voltage V_s decreases. This leads to a decrease in the actual ratio.

3. What is effect of the secondary burden on the ratio error?
a) ratio error is constant with secondary burden
b) ratio error decreases with secondary burden
c) ratio error increases with secondary burden
d) depends on the supply voltage
Answer: c
Clarification: As the secondary burden is increased, the ratio error also increases and becomes more negative. Ratio error varies linearly with respect to the change in the secondary burden.

4. V_p is leading in phase, while V_s is lagging in phase.
a) True
b) False
Answer: a
Clarification: As the secondary burden is increased, winding voltage drop increases. Voltage V_p is leading in phase while V_s is lagging in phase. As a result the phase angle increases with the secondary burden.

5. What is the effect of p.f. on secondary burden?
a) I_p shifts towards I_o
b) I_p deviates from I_o
c) I_p is independent of I_o
d) I_p and I_o cancel eachother
Answer: a
Clarification: When the power factor of the secondary burden is reduced, I_p shifts towards I_o. Voltages V_p and V_s come closer to E_p and E_s.

6. How is the transformation ratio dependent on the secondary burden?
a) decreases
b) increases
c) remains constant
d) depends on the supply
Answer: b
Clarification: As the primary voltage V_p is constant, the induced primary e.m.f E_p is reduced. Similarly the secondary voltage V_s is reduced with respect to E_s. As a result the transformation ratio increases.

7. Decrease in p.f. makes V_s to lead V_p.
a) True
b) False
Answer: a
Clarification: As the power factor is decreased, Vs leads in phase while V_p decreases in phase. Thus the phase angle reduces with the decrease in power factor (lagging).

8. At constant voltage how is frequency affected by flux?
a) decreases with an increase in flux
b) increases with a decrease in flux
c) remains constant
d) depends on the current
Answer: b
Clarification: When frequency is increased at a constant voltage, the flux decreases. Voltage ratio decreases as the magnetizing and iron loss components of current are reduced.

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