Which method can be used to test if an object is ferrous?

Using a tester magnet to determine if an object is ferrous is effective because ferrous materials, which contain iron, exhibit magnetic properties and will be attracted to a magnet. When the tester magnet approaches a ferrous object, it will cling to or exert a force towards it, confirming its ferrous nature.

The other methods mentioned serve different purposes. Radiographs are typically used for imaging and do not provide information about the magnetic properties of materials. Metal detectors can detect various types of metals, but they might not distinguish between ferrous and non-ferrous materials clearly, as they primarily identify the presence of metallic objects rather than their specific properties. A ferromagnetic detection system, although designed to identify ferromagnetic materials, is typically more complex and may not be as straightforward as using a simple tester magnet for everyday ferrous testing. Thus, the tester magnet is the most direct and practical choice for this purpose.