🔍 Key Concepts

• Combustible gas indicator internal measuring principle • How changing electrical resistance can be used to detect gases • Difference between chemical absorption vs. electrical measurement circuits

💭 Think About

• Think about whether these instruments usually depend on a chemical color change, a mechanical device, or an electrical circuit to read gas concentration. • Ask yourself which choice is commonly associated with measuring very small changes in resistance inside sensing instruments. • Consider which options sound like general descriptions of materials versus a well-known type of circuit used in precision measurement.

✅ Before You Answer

• Identify which option refers to a specific type of electrical measuring circuit, not just a substance or container. • Check which choice is commonly used in many types of sensors and meters to detect small changes. • Eliminate answers that sound like they would only store or absorb gas rather than measure it.