Basic Qualification · B-005 Basic electronics and theory · B-005-011-002
How can a transformer with two windings change impedance?
- A By matching winding resistance to impedance
- B By carrying different voltages and currents in each winding
- C By using the correct magnetic coupling between windings
- D By allowing the difference to be dissipated in core losses
Correct answer: B — By carrying different voltages and currents in each winding. From the official ISED question bank, verified word for word.
Why
A transformer changes impedance because its two windings carry different voltages and currents; when the voltage steps up, the current steps down in proportion, and since impedance is the ratio of voltage to current, this shift alters the apparent impedance seen by the source. The full explanation — and one for every question — is in Pro.
Practise this section
The theory: Ohm's law, power, series and parallel circuits, AC and DC, frequency and wavelength, decibels, and the metric prefixes the exam leans on.