Deep Dive: G4E10
The correct answer is B: To prevent discharge of the battery through the panel during times of low or no illumination. Why a series diode should be connected between a solar panel and a storage battery being charged by the panel is to prevent discharge of the battery through the panel during times of low or no illumination. Without the diode, the battery would discharge through the panel when the panel voltage is lower than battery voltage. For amateur radio operators, this protects the battery. Understanding this helps when using solar panels.
Why Other Answers Are Wrong
Option A: Incorrect. Series diode doesn't prevent overload by regulating voltage - diodes don't regulate voltage, they just block reverse current. Voltage regulation isn't the purpose. Option C: Incorrect. Series diode doesn't limit current to a safe value - diodes have minimal voltage drop, they don't limit current. Current limiting isn't the purpose. Option D: Incorrect. Series diode doesn't prevent damage from excessive voltage - diodes don't limit voltage, they just block reverse current. Voltage protection isn't the purpose.
Exam Tip
Series diode purpose = prevent battery discharge through panel. Think 'S'eries 'D'iode = 'S'tops 'D'ischarge. Prevents battery from discharging through panel when panel voltage is lower than battery voltage. Not voltage regulation, not current limiting, not voltage protection - just discharge prevention.
Memory Aid
Series diode purpose = prevent battery discharge through panel. Think 'S'eries 'D'iode = 'S'tops 'D'ischarge. Prevents battery from discharging through panel when panel voltage is lower than battery voltage. Essential for solar charging.
Real-World Example
You connect a solar panel to charge a battery. Without a series diode, when the sun goes down and panel voltage drops below battery voltage, the battery would discharge through the panel. A series diode blocks this reverse current, preventing battery discharge. This is essential for solar charging systems.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G4E
Reference: 2023-2027 Question Pool · G4 - Amateur Radio Practices
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G4E topic.