ESA Certified Alarm Technician Practice Exam

Electrical transformers only function with which type of current?

1. DC

2. AC

3. RF

4. Pulse

The correct answer is: AC

Transformers are devices that transfer electrical energy between two or more circuits through electromagnetic induction. They are designed to operate specifically with alternating current (AC) because AC constantly changes direction, which creates a varying magnetic field around the coils of the transformer. This varying magnetic field is essential for inducing voltage in the secondary coil, allowing the transformer to increase or decrease voltage levels as needed. In contrast, direct current (DC) flows in a single direction and produces a steady magnetic field, which does not induce voltage in a secondary coil effectively. As a result, transformers are not suitable for use with DC. Other forms of current, such as radio frequency (RF) or pulsed signals, may not provide the sustained, periodic changes in current necessary for efficient transformer operation. Thus, the unique properties of AC make it the only type of current that allows transformers to perform their function effectively, confirming that the correct answer is indeed AC.