What is the primary purpose of a transformer in an electrical circuit?

• A. To store electrical energy for later use
• B. To increase the frequency of the electrical signal
• C. To change the voltage level of $\mathrm{AC}$ between circuits
• D. To convert $\mathrm{AC}$ to $\mathrm{DC}$

Answer: (C)

Verified step by step guidance

1. Understand that a transformer is a device used in electrical circuits primarily to modify voltage levels without changing the frequency of the alternating current (AC).
2. Recall that transformers operate on the principle of electromagnetic induction, where a changing current in the primary coil induces a voltage in the secondary coil.
3. Recognize that transformers do not store electrical energy; instead, they transfer energy from one circuit to another through magnetic fields.
4. Note that transformers cannot convert AC to DC; that function is performed by rectifiers.
5. Conclude that the primary purpose of a transformer is to change the voltage level of AC between circuits, either stepping it up (increasing) or stepping it down (decreasing) depending on the turns ratio of the coils.