🔍 Key Concepts

• Differences between lead-acid and nickel-cadmium (Ni-Cd) batteries • What a hydrometer actually measures and when it can be used • Which instruments measure voltage, current, and resistance and how that relates to state of charge

💭 Think About

• Think about whether a sealed Ni-Cd battery gives you access to any liquid inside that you could test • Consider which battery types rely on electrolyte specific gravity to check state of charge, and which do not • Ask yourself which electrical quantity (voltage, current, resistance) changes in a way that can be used as an indirect indicator of state of charge in a sealed battery

✅ Before You Answer

• Verify whether sealed construction allows you to measure electrolyte properties directly • Match each instrument to what it measures: potentiometer, voltmeter, ammeter, hydrometer • Eliminate any tool that requires opening or sampling from inside the battery case of a sealed Ni-Cd battery