Which device produces its own electricity?

Which device produces its own electricity?

• A. Thermistor
• B. Oximeter
• C. Piezo-electric crystal band
• D. Actigraph

Answer: (C)

The main idea is energy sources: some devices harvest energy from their environment or user actions, rather than relying on a traditional battery alone. A piezo-electric crystal band uses the piezoelectric effect, which converts mechanical stress from movement into electrical energy. When you move, the crystal deforms and generates a small electrical voltage that can power or supplement the device, allowing it to produce its own electricity. Thermistors are passive components whose resistance changes with temperature; they don’t generate power. Oximeters require a power source to drive their light source and photodetector to measure oxygen saturation, so they don’t self-power. Actigraphy devices are typically powered by batteries and measure movement with accelerometers; they don’t harvest energy from motion.

The main idea is energy sources: some devices harvest energy from their environment or user actions, rather than relying on a traditional battery alone. A piezo-electric crystal band uses the piezoelectric effect, which converts mechanical stress from movement into electrical energy. When you move, the crystal deforms and generates a small electrical voltage that can power or supplement the device, allowing it to produce its own electricity.

Thermistors are passive components whose resistance changes with temperature; they don’t generate power. Oximeters require a power source to drive their light source and photodetector to measure oxygen saturation, so they don’t self-power. Actigraphy devices are typically powered by batteries and measure movement with accelerometers; they don’t harvest energy from motion.