🔍 Key Concepts

• Surge (characteristic) impedance of a transmission line depends only on the line’s geometry and the properties of the insulating (dielectric) material • How conductor size and spacing between conductors affect capacitance and inductance per unit length • Role of the dielectric constant of the insulation in determining capacitance and thus impedance

💭 Think About

• Which answer choices talk only about physical geometry and material properties of the line itself, not operating conditions like applied voltage or RF frequency? • Look at ‘dielectric’ and ‘insulating material’—which wording correctly reflects that it’s the material’s property, not a distance, that matters? • Ask yourself: if you turned the power off (zero voltage), would these three factors still exist and still define the surge impedance of that line?

✅ Before You Answer

• Make sure the option you pick does not rely on operating voltage or current; surge impedance is a line property, not an operating condition • Confirm that all three items in the correct choice are independent physical characteristics of the cable construction (geometry + material), not how it’s being used • Check that the dielectric term refers to a material property (dielectric constant), not a spacing or shield description that doesn’t change the material itself