What is the main purpose of a transformer in electrical systems?

• A. To regulate current in a circuit
• B. To convert AC to DC
• C. To stabilize voltage levels
• D. To increase or decrease voltage on a circuit

Answer: (D)

Transformers are used to adjust voltage levels in a circuit by increasing or decreasing the voltage through electromagnetic induction between two windings. When AC flows in the primary winding, it induces a corresponding AC voltage in the secondary winding. The ratio of voltages is determined by the turns ratio: more turns on the secondary produce a higher voltage, fewer turns produce a lower voltage. Because power is roughly conserved (minus losses), changing the voltage also changes the current inversely, so a step-down reduces voltage but increases current, and a step-up does the opposite. In alarm systems, this is how the building’s 120-volt supply is transformed to low voltages like 12 or 24 volts needed by control panels and sensors. This is why the transformer’s core function is voltage adjustment. It does not regulate current directly, nor convert AC to DC (that’s the job of a rectifier), and it does not itself stabilize voltage under varying conditions—that role belongs to voltage regulators or other stabilization equipment.