Photovoltaic (solar) cells generate electrical power when illuminated. Which application most directly uses a photovoltaic cell as its energy source?

Introduction / Context:
Photovoltaic (PV) cells convert light into electricity. They are ideal where grid power is unavailable or inconvenient, and where small to large amounts of DC power are needed without moving parts. The question asks you to identify the application that uses a PV cell directly as its power source.

Given Data / Assumptions:

• PV cell provides DC power proportional to irradiance and area.
• Applications vary widely in power needs—from microwatts to kilowatts.
• Focus is on the primary, direct use of PV output as an energy source.

Concept / Approach:
PV is most useful where line power is impractical: remote telemetry, outdoor sensors, off-grid lighting, and satellites. A “remote power source” explicitly captures this use case. While some calculators are solar, the TI-92 specifically used batteries, and other listed items typically rely on conventional supplies or are not energy sources themselves.

Step-by-Step Solution:
Identify characteristic: PV supplies DC without grid connection.Map to applications: remote or off-grid devices benefit most.Compare options: only “remote power source” universally and directly fits PV usage.Conclude that the best answer is the remote (off-grid) power source.

Verification / Alternative check:
Field deployments (weather stations, IoT sensor nodes, rural lighting) commonly use PV plus batteries for energy autonomy, validating the selection.

Why Other Options Are Wrong:

• Automobile horn: Requires high instantaneous current from vehicle battery.
• TI 92 calculator: That model is battery-powered; not a standard PV application.
• Magnetic field detector: A sensor function, not an energy source description.
• Crystal microphone preamp: Typically powered by batteries or phantom power, not PV specifically.

Common Pitfalls:

• Assuming all calculators are solar; many are not.
• Confusing sensors with power sources.

Final Answer:
a remote power source