Transformer MCQ's

1) A Transformer is designed to be operated on both 50 & 60 Hz frequency.For the Same rating, which one will give more out put; when,

            a) Operates on 50 Hz  

            b) Operates on 60 Hz

XL = 2πfL = 2 x 3.1415 x 50 x 1.2 = 377 Ω , XL = 2πfL = 2 x 3.1415 x 60 x1.2 = 452.4 Ω

2) In a Transformer , The primary flux is always _________ the secondary ( flux).
            a) Greater then
            b)Smaller then
            c) Equal
            d) Equal in both step up and Step down Transformer

3) What would happen if we operate a 60 Hz Transformer on 50 Hz Source of Supply.(and how can we do that?

a) Current will decrease (so increase the current)

b) Current will increase ( so decrease the current)

c) Current will be same in both cases.

d) No Effect (We can do that without changing anything)

4) A Step-Up Transformer which has 110/220 turns.What would happen if we replace it with 10/20 turns? (because Turns ratio would be same in both cases)

            a) induced E.M.F wold be same 
            b) Induced E.M.F would be decreased

5) The rating of transformer may be expressed in ____________.
            a) kW
            b)kVAR 
            c) kVA

6) What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage?

           a) Current will be too much high

           b) Transformer may start to smoke and burn

          c) Eddy Current and Hysteresis loss will be excessive

7) What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 5 Hz (frequency) source of the same voltage?

            a) Current will be too much low 
            b) Transformer may start to smoke
            c) Eddy Current and Hysteresis loss will be excessive

8) A Step Up transformer _____________.

            a) Step Up the level of Voltage     

            b) Step down the level of current      

            c) Step up level the power

            d) Step up the level of Frequency  

            e) a and b

9) An Auto-transformer (which has only one winding) may be used as a ______?

            a) Step-Up Transformer                                

            b) Step-Down Transformer

            c) Both Step-Up and Step-Down transformer

10) Impedance Ratio of a transformer is equal to _____________.

            a) Square of turns ratio
            b) Turns ratio
            c) 1
            d) Infinite

11) For actual transformers with higher load, leakage flux is prominent

            a) True 
            b) False

12) Dimensions of rate of change of flux are equivalent to those of

            a) voltage
            b)current 
            c) 1/charge
            d) charge

13) Transformer have zero voltage regulation at
            a) Leading power factor                                

            b) Lagging Power Factor                                
            c) Unity PF