Question

The quantity that remains unchanged in a transformer is

• A. Voltage
• B. Current
• C. Frequency
• D. None of these

Answer 1

The correct option is C

Frequency

The explanation for the correct option:

In the case of option C,

1. A static device that aids in the conversion of electrical power from one circuit to another while keeping the frequency constant is known as a transformer
2. It is used to increase or decrease the voltage but only in direct proportion to the current ratings.
3. The frequency in a transformer is kept constant to avoid hysteresis and eddy current losses.
4. Thus, $\mathrm{frequency}\mathrm{at}\mathrm{input}=\mathrm{frequency}\mathrm{at}\mathrm{output}$.
5. As supply frequency is constant so the output frequency will also be unchanged.

The explanation for the incorrect options:

In the case of option A,

1. Using the mutual induction principle, a transformer transforms an alternating potential difference from one value to another of a larger or lower value.
2. Therefore, although current and voltage in a transformer fluctuate, the frequency does not.

In the case of option B,

1. A transformer uses the mutual induction principle to change an alternating potential difference from one value to another of higher or lesser value.
2. In a transformer, current and voltage fluctuate but frequency does not.

In the case of option D,

1. As we got the right answer option C that frequency remains unchanged in a transformer.
2. so, this is not the case here.

Hence, option C is the correct answer.