🔍 Key Concepts

• Dielectric constant (relative permittivity) is defined relative to a vacuum • Dry air behaves almost the same as a vacuum for many electrical calculations • Values much larger than 1 (like 10, 100, 1000) usually belong to solid insulators such as ceramics or certain plastics

💭 Think About

• Ask yourself: by definition, what value is assigned to a perfect vacuum when we talk about relative permittivity? • If dry air is treated nearly the same as a vacuum in basic radio/electrical theory, would its dielectric constant be very close to that reference value, or much larger? • Compare: typical dielectric constants of common materials (water ~80, glass ~4–7). Which option is consistent with something almost identical to a vacuum?

✅ Before You Answer

• Verify that relative permittivity of a vacuum is the baseline value by definition • Confirm that dry air’s dielectric constant is only slightly different from that of a vacuum • Eliminate choices that represent values typical of high‑K dielectric materials, not gases like air