TOPIC- Transformer
Q.1 Which among the following is true about transformers?
a) Transformers are used to convert low alternating voltage to a high alternating voltage
b) Transformers are used to convert low alternating current to a high alternating current
c) Transformers are based on the phenomena of mutual electric field
d) Transformers are used only for low alternating voltage
Answer a)
Concept: Transformers are used to convert low alternating voltage to a high alternating voltage and vice versa. Transformers are based on the phenomena of mutual induction. A transformer consists of a soft iron coil with two coils wound around it which are not connected to one another. The other statements are not valid.
Q.2 The efficiency of a transformer is the ratio of output power to input power.
a) True
b) False
Answer- a)
Concept- Yes, the efficiency of a transformer can be determined by taking the ratio of output power to input power. Transformers are the most highly efficient electrical devices. Most of the transformers have full load efficiency between 95% and 98.5%.
Q.3 Which of the following is usually taken to make the core of a transformer?
a) Aluminum
b) Copper
c) Soft iron
d) Hard iron
Answer: c
Concept : Core of a transformer is used to transfer the flux produced by primary coils of transformer to secondary coils of a transformer. Therefore, the core of a transformer is made of soft iron because it has high permeability so it provides complete linkage of magnetic flux of the primary coil to the secondary coil.
Q.4 Current remains unchanged in a transformer.
a) True
b) False
Answer: b
Concept: No, this statement is false. The quantity that remains unchanged in a transformer is the frequency of the input alternating current. Frequency of the alternating current at input = Frequency of the alternating current at output.