Basic Qualification · B-008 Interference and suppression · B-008-002-010
One method of preventing RF from entering a stereo set through the speaker leads is to wrap each of the speaker leads:
- A around a wooden dowel
- B around a ferrite core
- C around a copper bar
- D around an iron bar
Correct answer: B — around a ferrite core. From the official ISED question bank, verified word for word.
Why
Wrapping speaker leads around a ferrite core works because the ferrite acts as a magnetic sponge that soaks up unwanted radio frequency energy, stopping it from turning into crackling noise in your stereo. The full explanation — and one for every question — is in Pro.
Practise this section
When things interfere: harmonics, overload, RFI to and from your station, filters, ferrites and how to fix the neighbour's TV.