🔍 Key Concepts

• Insulation resistance and what it measures in electrical systems • Which instruments are designed to measure very high resistance values (in megohms) • Typical uses of magnetos, dynamometers, and rheostats

💭 Think About

• Which of these devices is specifically built to measure resistance, and not to generate power, control current, or measure force? • When checking insulation, are you dealing with low resistance or extremely high resistance between conductors and ground? • Does the instrument’s name hint at the size/range of resistance it measures?

✅ Before You Answer

• Identify which option is an instrument for measuring electrical resistance rather than controlling or producing it • Recall that insulation resistance is normally measured in megohms (MΩ), not in ohms • Eliminate any devices whose primary function is mechanical measurement or power generation rather than resistance testing